It would be impossible to tell the story of Patek Philippe’s history in the perpetual calendar chronograph without telling the story of the incredible Stern family and its masterful guidance of Patek to become the single most predominant high watchmaking maison in Switzerland. The perpetual calendar chronograph was intrinsically linked to the realization of this goal and would become the single most identifiable calling card for the brand that many consider the greatest in the world.

Without retelling the entire history of Patek suffice it to say that it was founded in 1845 by Antoine Norbert de Patek and Adrien Philippe. In 1932 the company was acquired by Charles and Jean Stern. In 1958 Charles’ son Henri who had been Patek’s importer to the United States succeeded him as president and in turn his son the now legendary Philippe Stern took the Patek’s reigns in 1977.

Henri Stern (right) and his son, Philippe Stern (circa 1970s)

In 2009 Philippe Stern’s son Thierry was made president of the company. And it is with the Stern family, specifically Charles Stern that the story of Patek Philippe’s creation of the world’s first serially produced perpetual calendar chronograph the 1518 began. It is under Charles and Henri’s stewardship that the brand created what is today the most sought-after watch featuring this complication, the 2499. It is while managed by Henri and Philippe Stern that Patek created the modern classic 3970 and its the wildly ambitious split seconds chronograph version, the 5004. And it is thanks to the brand’s current leader that Patek realized what is in my opinion the most beautiful classic watch of all time, the 5970, as well as the current in-house movement powered 5270 and its split seconds equipped sibling, the 5204.

Philippe Stern (left) and his son, Thierry Stern (circa 2000s)

1941-1954 Patek Philippe 1518

• 281 watches

• Mostly yellow gold

• Aprox. 55 pieces in rose gold

• 4 pieces in steel

• Rumored 3 pieces steel and rose gold

Ref. 1518 (image: Christie’s)

The world is deep in the throes of the Second World War the United States already at war with Germany will declare war on Japan following the bombing of Pearl Harbor on December 7th. Hardly a year when complicated Swiss watches were most in demand.

Perhaps motivated by the necessity to demonstrate great creativity in face of challenging times, Patek Philippe launches two of the most ground breaking wristwatches in history. You can almost imagine brothers Charles and Jean Stern whose famous dial making family took over Patek Philippe a mere nine years ago concluding that in adverse times they had to be more daring and inventive than ever before. The first of these two watches is the 1526, the world’s first serially-made perpetual calendar. The second and perhaps even more famous is the 1518, the world’s first serially-produced perpetual calendar chronograph. As Ben Clymer writes in his excellent Reference Points article for Hodinkee, “Not a single other manufacture even attempted a perpetual calendar chronograph for another half century.” You can get that great read here.

The 1518 is in every way the Primus, the Alpha, the unequivocal first of its kind. It would define the aesthetic and technical blueprint of every single perpetual calendar chronograph that would come after. And even in instances where the design or layout of this complication differs from this watch, be it double retrograde as with Roger Dubuis or triple in-line windows as with Patek, it is fair to say these designs are a reaction to the iconic status of the 1518. The case of the 1518 is relatively straightforward. It is features straight thin lugs, a thin slightly concaved bezel, a large winding crown and rectangular chronograph pushers, all made by Georges Croisier.

But it is in the design that it is so iconic. The 1518 created the now familiar layout for perpetual calendar chronograph information, with day and month in two windows beneath the 12 o’clock index. The perimeter of its dial features at its outermost edge a base 1000 tachymeter scale – this is actually quite amusing that in the context of 1941 they thought they might need to time objects up to this speed – and an ingenious chemin de fer track with marks for the 1/5th of the second (corresponding with the Valjoux movement’s 18,000 vph) at the outer edge and for minutes/seconds on its inner edge. A subdial at 9 o’clock provided a reading for continuous seconds and a subdial at 3 o’clock displayed the chronograph minute counter.

Perhaps the most inventive indication was found at 6 o’clock which provided a reading for both the date and the phase of the moon in a half moon shaped space across the upper half of this subdial. The entire dial was made from grand feu enamel as were the discs for the day and month and as well as the moon phase indicator. The subdials which were sunken were also made from seperate pieces of enamel. The now famous indexes consisted of a full host of applied Arabic indexes minus 3,6 and 9 which were occupied by subdials. The 5 and 7 indexes were replaced with applied dot markers to provide more breathing room for the display at ‘6’.

The movement powering the 1518 was the famous Valjoux Caliber 13, which also powered the brand’s famous reference 130, its first serially produced wristwatch chronograph. However the addition of the perpetual calendar module was performed by Victorin Piguet. A total of 281 watches were made and famous owners included King Farouk of Egypt, the King of Jordan and the fabled watch collector Henry Graves.

Movement driving the ref. 1518 (image:
One of only four steel Patek Philippe ref. 1518s that is publicly known today to have been completed (Image: John Goldberger)

The watch was made in yellow and rose gold with a small handful of four incredibly valuable steel watches which are chronicled in our friend John Goldberger’s book on Steel Patek Philippe watches. But the steel watches are conceivably not the rarest 1518’s around. In 1942 it was said that Patek made three very special two-tone watches in steel and rose gold. For many years it was believed, now proven erroneously, that one of these two-tone watches was the property of King Michael I of Romania; however a closer examination of a 2017 color photo of the monarch wearing his 1518 reveals it to be a full gold model.

1950-1985 Patek Philippe 2499

• 349 watches

• Yellow, white and rose gold

• Two watches in platinum; one in the Patek collection the second sold at auction for Patek’s 150th anniversary in 1989 and purchased by Eric Clapton. Auctioned by Christie’s in 2012 for US$3.6 million

Ref. 2499

In 1951 America has become the most affluent nation on the planet, and New York the epicenter of wealth and excitement. The ’50s are saw an influx of deposed monarchy, artists and other glitterati all migrate to Manhattan, while the creative nerve center of the art world also shifted there with the rise of the American Abstract Expressionist movement whose hero is Jackson Pollock. On the literary scene J.D. Salinger’s genre defining novel A Catcher in the Rye created an uproar. Bill and Babe Paley held court amongst the jet set which included a fledgling author named Truman Capote who had just published The Grass Harp, while the anointed kings of high society Oleg and Igor Cassini would hold court deep into the night at the Stork Club and the El Morocco. And it was into this world of promise, change and optimism that Patek Philippe brought forth what is commonly considered to be the single greatest wristwatch of all time, the perpetual calendar chronograph known in collector speak as the two-four, nine-nine.

John Perona (right), owner of El Morocco, celebrating New Year's Eve with guests in 1951 (image: Bettmann/CORBIS)

The reference 2499 was an altogether bolder timepiece than its serene poised predecessor the 1518. Interestingly there was a four-year period of model overlap where you could buy either. And what a choice you had. If the 1518 evoked the cool icy beauty of Grace Kelly, then the 2499 had all the Latin tempestuousness of the Gabor sisters, Claudia Cardinale and the onomatopoeic wonder known as Gina Lollobrigida, all wrapped into one. First, at 37.5mm in diameter, it was far more imposing that its 35mm ancestor and considered by many the perfect size to this day.

Ref. 2499

Second, the watch’s sexy stepped lugs injected a healthy dose of concupiscent design dynamism. The bezel while also concaved, was executed with a more expressively attenuated curve. The watch was just a little bit extra in every regard. The increase in size allowed for a dial with larger more visible indications and a bit more breathing room than was evident with the 1518. The watch featured the same Valjoux Caliber 13 based movement and featured the same tell-tale traits of the reset pusher being further positioned from the crown than the start-stop pusher, something that became more apparent with the switch to smaller round pushers in the 2nd to 4th series of its life span. The four different series of 2499 watches can be distinguished in the following way.

First Series 1950 to mid 1950s

The most valuable series of 2499 features Arabic markers, a tachymeter scale and rectangular pushers. What is the most valuable 2499 in the world? Based on the amount it achieved at auction it would be this first series 2499 double signature watch, the only one known in existence to feature an Asprey signature which sold for USD 3,879,843 at Sotheby’s GE1804 ‘ASPREY’ auction.

Lot 220 Patek Philippe ref. 2499 retailed by Asprey; yellow gold perpetual calendar chronograph with moon phase, made in 1952.
One-of-a-Kind Asprey-Signed Ref. 2499

Second Series 1955 to 1960s

The second most valuable series of 2499 features Arabic or baton markers for the hours, a tachymeter scale and round pushers. The second series watches could also be double signature watches, check out this incredible 2499 second series with Tiffany stamped dial on a bracelet here chronicled by our friend SJX.

Ref. 2499 in pink gold, second series (image: Christie’s)

Third Series 1960-1978

This series is the most common and does not have a tachymeter, uses baton markers for the hours, round pushers but retains the acrylic crystal of its predecessors.

Ref. 2499 in rose gold, third series (image: Phillips)

Fourth Series 1978-1986

This series is similar to the third series but now features a sapphire crystal. In 1985 just before the end of the production run the Stern family commissioned two platinum watches to be made. One was kept in the Patek Philippe collection while the other was auctioned as part of the celebrations for the brand’s 150th anniversary. That watch ended up in the hands of renowned Patek collector Eric Clapton before surfacing at auction at Christie’s thanks to Aurel Bacs and in 2012 achieved US$3.63 million including buyer’s premium.

Ref. 2499 in platinum case, fourth series

In 1986, a year before the release of the film Wall Street, the world is a amid a heady opiate period of affluence and wealth. Men are still attired in classic suits for work and similarly, the wristwatch is the apogee of their self-expressive style. But watches are still a full decade and a half from swelling in proportion, and the idea of elegance rules the day.

1985-2004 Patek Philippe 3970

4,200 watches

Patek Philippe Ref. 3970

Accordingly tasked with designing the successor to the iconic 2499, Philippe Stern makes the decision to reduce the size of the case to 36mm, down from 37.5mm. Says famed watch collector and author John Goldberger, “In the context of the ’80s this was the right size for the watch. Companies such as Blancpain which had re-entered the market as a specialist in mechanical complications was making the majority of its cases in 33mm. Says Nick Foulkes, “Knowing Philippe Stern, he was almost certainly motivated to assert a new level of expertise at Patek and the idea of making a complicated perpetual calendar chronograph in a smaller case size that was 36 mm was most certainly an expression of the manufacture’s savoir faire. Following the Quartz Crisis this was an important statement of ability. In addition, he felt that this was the perfect size from an aesthetic perspective and the fact that it is 1mm larger than the 1518 and 1.5mm smaller than the 2499 placed it in the perfect sweet spot for him and for the period in which the watch was born.”

Stern who would already be well on his way to becoming one of the most revered near mythological figures in the watch industry would create a watch that was Zen reductionist purity in extremitas. Says Foulkes, “That is what is so appealing about the 3970, it rejects any form of unnecessary flourish and focuses on the perfect execution of the perpetual calendar chronograph reduced to its barest essence.” Everything about the 3970 is discreet and understatedly appealing.

Ref. 3970, with 24-hour at '9', leap year at '3', triangles at each hour marker (Image: Christie's)

The baton-shaped hour markers are lean and attenuated. There is no tachymeter in existence. The perimeter of the dial features a hash marked seconds track, with tiny arrows at the end of each marker pointing to subtle Arabic seconds index. The case is smooth and round. The lugs are thin and so subtly stepped that it is possible to miss this detail at first look; the pushers are round.

Ref. 3970, with leap year indication at '3' subdial (Image: Christie's)

Indeed the easiest way to tell the difference in a quick glance between the 4th series 2499 and the 1st series 3970 is that for the first time, the new watch featured an indication for leap year, subtly integrated into the chrono minutes counter at 3 o’clock, as well as a 24-hour indicator integrated into the continuous seconds at 9 o’clock. This display was critical as adjusting the calendar while the movement was amid its change-over period from one date to the next could damage it.

Ref. 2499 4th series
Ref. 3970

Inside the watch and featured for the first time in a Patek Philippe was one of the most venerable and legendary calibers in watchmaking history, the Lemania 2310. This movement dates back to 1942 and was a joint project between Lemania and Omega. This movement rebadged as the caliber 321 was featured in every Omega Speedmaster from the 1957 CK 2915 to the 1968 145.012-68 and was famously beating inside every Speedmaster that went into space.

Lemania 2310 movement in the ref. 3970, as the Cal. CH 27-70 Q (image: Christie’s)

First Series 1986

100 watches

Ref. 3970, first series (image: Christie’s)

The first series 3970 watches are characterized by having subdials that are of complementary but non-matching tone relative to the dial (however, this dial is not entirely exclusive to the first series). The easiest way to distinguish a first series watch is that they came equipped with a snap-on solid case back which made them non water resistant. The first series watches were made exclusively in yellow gold with an opaline dial with applied yellow gold baton markers and yellow gold leaf/dauphine hands. The reference 3971 was sold concurrently and was exactly the same watch but with a snap-on display back which is chronicled here in Ben Clymer’s excellent Reference Points article on the Patek perpetual chronographs.

Second Series 1986-1991

Ref. 3970, second series (image: Bonhams)

The second series of 3970 watches feature a screw-down case back. For this second series of watches, you could order it with either a solid screw-down case back, in which case it would be designated reference 3970; or with a screw-down sapphire case back, in which case it would be designated reference 3971. In general, the second series 3970 differs from the first series 3970 in that the subdials are now the same color as the dial. However, there are instances where the earlier dial appears on the second series watches such as on this 3971 dated, based on the Patek extract from the archive, to 1990 and which also comes equipped with a second screw-down solid case back dated to 1999.

Ref. 3971 (images:

The second series 3970 watches could also be ordered on a bracelet as reference 3970/002. However in this instance the watch would no longer have the traditional lugs but be fitted with an integrated precious metal bracelet as seen here, making it in essence a totally different model from the traditional 3970.

Ref. 3970 with case and integrated bracelet in yellow gold (images: Robert Maron)
Ref. 3970 with case and integrated bracelet in white gold (images:

Third Series 1991-2004

The difference in the third and most common series of watches is the designation “E” for Etache or Waterproof after the model number. Watches all now come with both a sapphire screw back and a solid screw back, a practice which would continue with the subsequent models. The idea is that owners could have the option of viewing their sumptuously decorated Geneva Seal movement, a tradition that reaches all the way back to the 1518 or could personalize the solid case back with an inscription, initials or coat of arms. The front of the watch differs as well in that all third series watches feature thinner baton hands and long, more attenuated markers replete with sharp diamond tips. These markers now almost touch the bolder arrow shaped printed indicators that point at the Arabic markers for each 5th second on the seconds track.

Ref. 3970 third series (image:

End-of-Series Watches and Special Order Watches

In 2003, just before the 3970 was discontinued, several end-of-series special order watches were made including this incredible Arabic index platinum model. Note that the dial features the off-color subdials normally associated with the first series watches, and stunning black rhodium baton-shaped later series style hands and unique Arabic indexes. Indeed, on close inspection this watch appears to be a 3970 with a platinum 5004 dial and 3970 hands.

Patek Philippe Ref. 3970 Platinum (Image:

Eric Clapton’s name again comes up when we discuss the unique execution 3970 watches. It is around 2008 when Eric Clapton started to amass a collection of 3970 and 5004 watches in a very particular dial execution that you can say had a major impact on the design of the 3970’s successor, the 5970. Throughout both their life spans, the 3970 and its split seconds chronograph cousin the 5004 never featured a tachymeter. The exception to this is in the unique execution dials of both watches made for rock legend Eric Clapton. These dials feature an Arabic 12 o’clock index, sensuous applied dot hour markers and feature both a full seconds track and a full tachymeter scale.

Custom-dial ref. 3970 for Eric Clapton
Custom-dial ref. 5004 for Eric Clapton

But how do you fit this scale into a 36mm watch that already shows so much information and that features a subdial at 6 o’clock for both the date and moon phase indication? The solution is to me one of the greatest acts of dial design magic chez Patek. The tachymeter track is abbreviated so that it disappears into the date ring from the dates of the 11th to the 21tst. There are tiny markers for 130 and 110 and nothing in between. But from a visual perspective the speed between 130 and 110 can still be easily approximated depending on where the chronograph hand lands when you stop it. This allows you to place the minutely indexed full seconds track to the exterior of the dial replete with full 1/5th of a second markers in accordance with the Lemania 2310’s 18,000 vibrations per hour speed.

It should be noted that the very first time Patek abbreviated a track to accommodate the date display was with the seconds track in some first or second series 2499 watches.

But this way of abbreviating the tachymeter was something never done before in either of the 3970’s predecessors. Looking at images of the 1518 you will see a fully articulated ring around the date indications at 6 o clock, a fully realized seconds track and the tachymeter placed to the exterior which makes it harder to read because the font for the speed is so small. The first two series of the 2499 use the same arrangement though some dials feature an open date display that merges into the second track. With the unique dials of the 3970 / 5004 the inversion of the seconds track and tachymeter means that the tachymeter gains far greater visibility and is much easier to use.

Ref. 1518
Ref. 2499 (2nd series)
Custom-dial 3970
Custom-dial 5004

It also means that the print for the tachymeter can be far bolder, expressing a more performance-oriented character for the watch. Clearly the scales used in these dials struck a chord with Thierry Stern because when it came time to design the 5970, he used this exact design.

London Exhibition Watches

The “Eric Clapton” style dial 3970 was revived in 2015 during the Saatchi Gallery exhibition for the brand’s 175th anniversary during which a stunning rose gold model of the 3970 was introduced featuring a black Arabic 12, applied dot index dial with tachymeter. If you look here at the images of the London Exhibition 3970 you will see that the dial is actually the same as the dial used in this 5004 made expressly for Eric Clapton.

Ref. 3970 re-issued for Patek Philippe’s 175th anniversary
Custom dial ref. 5004 for Eric Clapton

5020 cushioned shaped perpetual calendar chronograph 1993-1999

• Approximate number of watches 300

Ref. 5020 (image: Christie’s)

The Stern family clearly loves a cushion-shaped watch. This was aptly demonstrated in 2011 when Philippe Stern created a 16-piece limited edition of reference 3670A, a steel cushion-shaped chronograph featuring 16 new old stock Patek Caliber 13-130 movements based on the Valjoux 23 ebauche, the very same caliber that powered the brand’s hallowed and revered reference 130 chronograph. This was also demonstrated in the mid ’90s when Philippe Stern unveiled the reference 5020, a perpetual calendar chronograph featuring the same Lemania 2310-based calibre CH 27, now in an oversized cushion case. The watch was further distinguished by the use of applied Breguet-style numerals and Breguet-style hands.

Because of the model’s initial unpopularity it was discontinued after a couple of years and as such it is speculated that no more than 300 examples of this watch exists.

Eventually collectors must have come around to them, as the rarity of these watches has caused them to be auctioned for prices in the hundreds of thousands of US dollars.

5004 Perpetual Calendar with Split Second Chronograph 1994-2012

• All metals around 200 watches

• 50 end-of-series watches in steel with owners’ names engraved on the caseback

Ref. 5004

The 5004 is a watch that Philippe Stern pushed his team passionately for, a journey that was not without some massive hurdles. But first let me briefly explain what a split seconds chronograph is. It is a chronograph with seconds hands that run together. When you press the split button, integrated in the 5004 into the crown, the split seconds hand stops for you to record an interval time such as a lap time, while the chronograph seconds hand continues to march imperiously forward. Press the split button a second time and the split seconds hand instantly catches up with its still running sibling, which provided inspiration for this complication’s French name, “rattrapante” which means to “catch up.”

It is commonly known that the most challenging complication to craft is the minute repeater, a watch that plays the time in hours, quarters and minutes on wire gongs. However while many think the tourbillon is the second most challenging watch to fabricate, experts know that this is actually the split seconds chronograph. And the 5004 was no exception. Said Philippe Stern, “The problem was that the Lemania 2310 or CH 27, was never intended to be a split seconds chronograph. We had two major challenges. The first was the pinion that all the hands – hours, minutes, chronograph seconds and split seconds – had to be made even longer and we were really stretching the limits of what was possible. Even the slightest mistake it was easy to bend this pinion. And second thing was that the CH 27 would experience rattrapante drag each time the split seconds function was activated.”

Close up of Ref. 5004 (Image: Christie's)

What is ratrrapante drag? What allows the split seconds to catch up with the running chronograph seconds hand so quickly and effectively is a minute ruby roller attached to an arm and loaded with a spring. This ruby rolls around the circumference of a heart shaped reset cam attached to the chronograph wheel. When you press the split seconds button a mighty pincer-like brake stops the split seconds wheel. But at the same time the roller is tracing the shape of the reset cam the whole time, under the load of the spring so that the moment the split seconds wheel is released it can jump back to the correct position. The problem is that the force exerted on the heart cam by the jeweled roller can cause the entire chronograph mechanism to slow down or even stop. This is what is known as the dreaded rattrapante drag.

Patek’s solution to this issue was both beautiful and ingenious. It created a second mechanism known as an isolater, that sits on top of the split seconds brake. When the function is activated the isolater lifts the return lever off the heart cam so that there is no pressure placed on it. When the split seconds function is released it pushes the lever back into the heart cam so that it instantly resets. This mechanism is known amongst collectors as the “Octopus” because its shape resembles that of a the multi-tentacled sea creature.

The isolator for the split-seconds lever relies on an isolator wheel that is driven by an octopus wheel (O) (isolator wheel / splitseconds spring wheel) on the split-seconds column wheel and uncouples the split-seconds lever as soon as the split-seconds clamp (C) closes. Because the octopus wheel consistently rotates in the same direction, it always has to be returned to its home position together with the split-seconds lever; this is done by the isolator wheel spring as soon as the split-seconds clamp opens again.

The 5004 was a staggering demonstration of Patek Phillipe’s incredible technical mastery. The fact that Patek was able to keep the size of the watch at 36mm (though the case is thicker than the 3970’s) was an incredible expression of its confidence in mechanical complication’s enduring relevance.

The 5004 was launched in 1994, nearly a full decade after the debut of the 3970 and was only discontinued in 2012. It is said that Patek made around 12 watches per year so during its 17 year run that means that only 204 watches were made which seems too low. An additional 50 watches were made in steel to celebrate the end of series for this now mythological timepiece and each owner’s name was engraved in the back.

The dial of the 5004 is one of the most beautiful ever created by Patek, taking the Arabic indexes of the 1518 and the first two series 2499 watches and merging them with an otherwise classic minute and seconds track with slight abbreviation of the minute track to accommodate the date display from the 13th to the 19th. The steel watches feature a totally different dial characterized by baton markers. All models of the 5004 feature leaf shape hands. As mentioned there were several unique dial executions for the 5004. You can see Eric Clapton’s black dial, Arabic 12 and applied dot dial with tachymeter here.

There is also this incredible watch with a similar configuration only with a Roman 12 and incredible luminous hands and indexes here.

There was one unique watch created in titanium for the 2013 Only Watch Auction which achieved an incredible result of 3.98 million dollars.

Ref. 5004T, Only Watch 2013

2004-2010 Patek Philippe 5970

• 2,800 watches

• Rose and White gold the most common, made from 2004-2008 (1,000-1,250 each)

• Yellow gold the rarest and made only in 2008 (100-300)

• Platinum made from 2008-2010 (300-500)

Ref. 5970 Yellow Gold

In 2004 I attended my first Basel Fair and was stopped dead in my tracks at the Patek Philippe booth by a watch that was simultaneously an incredible tribute to the history of the brand’s perpetual calendar chronographs, yet a watch that was tantalizingly and confidently modern. It featured a bold tachymeter and leaf shaped hands and square pushers like the 1518 and the early 2499’s, and had a creative integration of the minutes, tachymeter and seconds scale with the date display that brought to mind the super racy unique dials created for Eric Clapton’s 3970 and 5004. And it featured the single sexiest lugs in Christendom, combined with a 40 mm case size. I was smitten. From that moment onwards I would see the 5970 in my dreams, just out of reach until one day half a decade later when I had saved enough money to finally afford one, the first and grandest realization of my loftiest horological dreams.

An exceptional instance of the Patek Philippe perpetual calendar chronograph ref. 5970 in platinum. This instance was sold by Phillips Watches at their Geneva Auction: FIVE in November 2017 for CHF 187,500 (Image:

I didn’t know it at the time but the 5970 is the very first watch designed by current Patek Philippe president Thierry Stern, the fourth generation in the Stern family to take the helm of the greatest jewel in Swiss high watchmaking’s crown. It is also to my mind the most beautiful and wearable classic watch ever created. However before I go into my rationale as to why, let’s find out more about Stern’s thought process behind the design of this modern icon.

Said Thierry Stern in an interview with Nick Foulke’s for Revolution found here, “Looking back I could see that it was a test to see if I could become an adult in terms of design at Patek. The only brief my father gave me was, ‘Ok, make your own choices.'” After thinking about it long and hard, Stern decided to create a watch that would represent a bridge between his father’s generation and his: “I decided to design a watch that could be worn by either my father or myself… For me it is one of the few pieces, perhaps the only pieces that is the mix of two generations of the Stern family.”

Stern began with one critical design criteria which was to make his watch 40 mm in diameter to aid visibility. Says Stern. “My key focus was legibility. For that I needed more space than the 3970 allowed. The indication of the day and month were giving me so much trouble that I came very close to including a magnifier on the glass to enable them to be read easily. But that would have been too radical. Instead, I worked to make it as simple as possible and we tried around 20 different dials.”

Next Stern brought back the tachymeter scale that was used to great effect with the Patek 1518 and the first two series 2499 watches. The tachymeter also served one other important purpose. That is to ensure the subdials of the watch did not feel stranded in the center of the dial. Nick Foulkes explains, “Thierry had to be careful that the subdials did not seem marooned in the middle of a comparatively empty dial. At 40mm the 5970 was by no means big for its day, but it allowed the sub-dials space to breathe; as a result the date on the subdial at 6 o’clock is noticeably more legible, as Thierry made that subdial bigger. However, any sense of agoraphobia is banished with the tachymeter that provides what is in effect a circular frame for the familiar yet subtly different layout.”

Ref. 5970 White Gold

It should be noted that the hands of the 5970 also quoted from Patek Philippe’s past. The 1518, 2499 and first two series 3970 watches all featured leaf-shaped hands. However with the last two series 3970’s these hands were replaced with the rather more minimalistic baton hands. Considering the wholly more sporty and aggressive nature of the 5970, it seems appropriate that Thierry Stern revived the more stylised and substantial leaf hands. Stern then complemented the decidedly more sporting nature of the 5970 with two more design elements. The first was the reintroduction of the more purposeful rectangular pushers that perfectly complemented the tachymeter and the larger case size. Patek had switched to round pushers beginning with the second series 2499 in the mid 1950s. The second was the creation of what I consider to be the most beautiful lugs to ever grace a watch with complication.

A Patek Philippe ref. 5970 perpetual calendar chronograph in 18k yellow gold sold by Christies for approximate USD 125,000 in 2011 (Image:

Patek Philippe has always been a maison that exhibited a design daring and flair related to its lugs. This is expressed with the flame lug watches such as the 2431 and the 1579 Spider lug chronograph.

Ref. 2431 “flame” lugs
Ref. 1579 “Spider” lugs
Ref. 5970 lugs

There is a certain genetic alliance between both these distinctively flared and faceted lugs and the lugs Stern designed for the 5970. He recalls, “The hardest thing to do was to create new lugs that were strong and yet refined. Production was a challenge at the time and when we did make a prototype that I liked, I was told that it would not be possible to realize in quantity. They were hard to polish, especially the angles. You had to respect them and they had to stay sharp after they were polished. But thanks to my own apprenticeship at Ateliers Reunis (at the time Patek’s case and bracelet workshop) I did not take no for an answer and in the end we found a solution.”

Here’s some further insight into the 5970. The rose and white gold watches were made concurrently from 2004 to 2008 and it is believed that 1,000 to 1,250 examples of each of these exist. The yellow gold version was made for one year only in 2008, making it the rarest of all metals with an estimated 100-300 created. The 5970 was produced in platinum for two years from 2009-2010 with an estimated 300-500 made. What’s interesting about the platinum watches is they are set apart from the other 5970s with two discreet but clear differences. The first is that each case is set with a diamond at 6 o’clock. And the second is that the marker for 120 appears on the tachymeter scale whereas in the other versions the word “Swiss” appears. In this case, “Swiss” is subtly integrated into the seconds track below. This is the only regular production 5970 where the 120 marker appears.

(From Left) A complete set of reference 5970s sold by Christie’s in white gold, rose gold, yellow gold and platinum, the latter with distinct tachymeter scale

The special edition and end-of-series 5970 has been the subject of some amount of study here at Revolution and you can click here to look at our article that chronicles the most famous of these watches.

2011-today Patek Philippe 5270

Ref. 5270 1R

In 2011 an important transition happened for Patek Philippe. It bid adieu to the much beloved Lemania 2310 powered 5970 and introduced the 5270, the very first Patek Philippe perpetual calendar chronograph in the brand’s history to be powered by an in-house movement. There were two factors underlying this. The first was that SWATCH Group owner Nick Hayek Sr had long publicized his intention to stop delivering movements to brands outside of the Group. The second was Philippe Stern’s long term objective to achieving full independence in manufacturing. This was clearly the impetus behind his creation of Patek Philippe’s incredible manufacture in Plan les Ouates, an investment his father Henri had reservations about; it was behind his push into silicon escapement components which freed him of reliance on SWATCH Group owned Nivarox and it was the motivation behind the creation of the in-house laterally coupled column wheel chronograph movement, the CH 29.

Ch 29-535 PS Q

This was not the brand’s first in-house chronograph. That status belonged to the caliber CH 28-520, an altogether sportier movement with automatic winding, a vertical clutch, silicon escapement and hairspring and a mono counter displaying elapsed hours and minutes together. But the CH 29 is a different animal altogether, a more refined elegant beast meant to continue in the tradition of the Valjoux 13 and the Lemania 2310.

The movement first made its debut in 2009, in of all things, a ladies’ chronograph. But it was clear from that moment that it was intended to do duty as the base for all of Patek’s manual-wind chronographs. Says Thierry Stern, “The advantage to the CH 29 is that it was designed from the ground up to function with a perpetual calendar as with the 5270 or even a perpetual calendar as well as a split seconds function as we offer with the 5204. In comparison we had to reverse engineer the capacity to have these functions with the CH 27.”

The new CH 29 was without a doubt a far more advanced and technically superior movement. First it beat at a far more modern 28,8000 vibrations versus the CH 27’s 18,000 making it far more stable against micro-shocks. Second it featured a precise jumping minute counter. While not the first chronograph movement to accomplish this – Lange and Chopard L.U.C had already achieved this – the CH 29 also featured six patents unique to Patek.

The first three related to the elimination of chronograph backlash. This happens when the teeth of the chronograph drive wheel and the chronograph seconds wheel mate imprecisely causing the chrono seconds hand to either leap forward or backwards, undermining its accuracy. Patek combated this with a patent on an optimized tooth profile, so the teeth of these wheels engaged better. Its second patent related to improved penetration adjustment between clutch and chronograph wheels. This allowed more precise adjustment of the depth engagement of these wheels, also a factor in back lash. And third it took a patent on the improved synchronization between clutch lever and blocking lever, which improved the interaction between the braking mechanism and the drive mechanism for the chrono so that the chrono seconds hand was stopped and started as accurately as possible.

The remaining three patents related to improving the reset function of the chronograph. Patent four was for a pierced out minute counter cam, patent five for self-setting return to zero hammers and patent six for hammers pivoted between jewels. These were all subtle improvements that collectively introduced a whole new level of function.

Regarding the design of the 5270, the watch has now undergone four incarnations and it is interesting to look at the progression related to this over the years. During this time design has changed only for the dial while the 41 mm case with flared lugs, in essence a larger size 5970 case, has remained the same.

2011 First Series no tachymeter

• White gold silver dial

Ref. 5270 (1st series) (Image: Michael Ashton Watches)

Ok the first thing you’ll immediately notice about the 5270 is the appearance of two windows at 4:30 and 7:30. The first provides an indication for leap year and the second provides an AM and PM indication to aid in setting your watch. These indications were previously integrated into the subdials at 3 and 9 o’clock respectively with the Lemania based watches and the new layout vastly improves ease of reading. Indeed, all-round legibility is vastly improved with bigger windows and indications. However the second thing you’ll notice is that the enlarged 3 and 9 o’clock subdials for chronograph minutes and continuous seconds both appear significantly below the horizon line between the crown of the watch and the 9 o’clock index.

This causes both subdials to drop well below into the lower half of the dial, which in turn pushes the large sized date/moonphase display at 6 o’clock to the bottom of the dial. Now this is entirely fine when the perimeter of the dial features a double layer chemin de fer minute and seconds track but no tachymeter. Though collectors were puzzled that the seconds track was divided into 1/5th seconds rather than 1/8th second to correspond to the movement’s vibrational speed. But things get a little bit more complicated when Patek decided to add a tachymeter back to the watch with the second series beginning in 2013.

2013 Second Series integrated tachymeter and seconds track with “Chin”

• White gold opaline dial

• White gold blue sunray dial in 2014

Ref. 5270G-013 in white gold case with opaline dial
Ref. 5270G-014 in white gold case with blue sunray dial

In 2013 Patek decided to add the sporty and wonderfully aggressive tachymeter scale back to their perpetual calendar chronograph. Because of the way the three subdials of the watch were compressed into the lower half of the dial, space between the date and a potential tachymeter was limited. Patek solved this issue by creating a single scale for minutes, seconds and tachymeter in one. This scale then ran in a semi-circle around the date indicator which formed what is now known in collectors-speak as a distinct “chin.” Whether you like this or not is a question of personal taste.

The “chin”

2015 Third Series classic tachymeter and seconds integration similar to 5970

Ref. 5270G-018

In 2015 the 5270 underwent yet another subtle design change. This time minutes, seconds and tachymeter scales in that order were restored as separate tracks for the dial which is to me far more pleasing to the eye and much easier to read. How did Patek get around the limited space for these tracks at the bottom of the dial? By using the same design ingenuity used for Eric Clapton’s unique dial 3970 and 5004 watches as well as by Thierry Stern in the 5970, by simply abbreviating the minute and tachymeter tracks from the 13th to the 19th.

As it is still relatively easy to understand which minute your watch falls in and what the approximate speed of something you are timing is, these scales are still perfectly functional. Indeed the 5270 even adds in the marker for 120, something not found on the gold regular production 5970s. The fractions of the second are relegated to the outer perimeter of the dial and not interrupted by the date display. With this third incarnation it seems that Patek got their perpetual calendar perfect again. But waiting in the wings would be two watches that would set an all-new level of desirability for the 5270.

2018 Fourth Series Gold on bracelet and Salmon dial with Arabic Indexes

Ref. 5270/1R with gold bracelet
Ref. 5270P-001 with salmon dial

While the rose gold black dial 5270 on bracelet is not precisely a fourth series watch in that its dial is identical to the third series model, it does add one incredible innovation to the mix and that is the pushers for correcting the calendar information are actually integrated into the bracelet, making them far easier to access. The rose gold black dial 5270 can be described as the single most sporty and sexy manual wind perpetual calendar chronograph in the brand’s history and at 41 mm with a substantial gold bracelet is not for the faint of heart. The white print contrasted by the jet black dial and rose gold hands, indexes, case and bracelet make it a terrifically alluring timepiece. It is my belief that this model is actually based on a special order 5970 with the same exact configuration, but how nice is it that Patek took what should in essence be a special order watch and made it available to the public.

But as dynamic as the rose gold 5270 on bracelet was, it was eclipsed at the 2018 Basel Watch Fair by another Patek 5270 that paid incredible tribute to the Stern family’s history with this complication and that is a platinum case watch with a stunning salmon dial. In the history of the Patek perpetual calendar chronograph salmon dials were reserved for very special watches. You can see an image of Eric Clapton’s salmon dial 3970 with Arabic 12 here.

And there were the platinum case salmon dial 5970 watches with Roman 12’s that were part of the end-of-series 4-watch box sets. Then there were the white gold salmon dial London Exhibition 5970s from 2015. But this was the first time that a salmon dial perpetual chronograph had been made as a general release.

Further the watch featured something not seen on a regular production perpetual chronograph since the 1950s and that was Arabic indexes which ended with the second series 2499 watches. The fact that Patek chose to revive these indexes here instantly made this new watch a cult collectible. Further, because of the size of the black rhodium treated Arabic indexes they serve to perfectly fill the larger empty space left across the top of the dial by relegating the three subdials below the horizon line. The result is the single most balanced and attractive 5270 in the model’s history. It is simply epic.

Ref. 5204: From 2012 – Present day

Ref. 5204

Launched in 2012, the 5204 perpetual calendar chronograph is replete with some very serious functional improvements to the 5004. The first is as described earlier: to overcome rattrapante drag, Patek had to create their now legendary Octopus isolator mechanism. Now it is important to understand that at the time of the 5004’s launch the Octopus was ground-breaking technology. There are two main springs in this Isolator system. The first is the spring for the split seconds brake which allows its clamping function. The second is the isolator wheel spring that sits on top of the split seconds wheel and necessitates a good bit of extra height. Now this is the important part. The springs of the isolator wheel and the springs of the split seconds brake act in opposite directions. That’s because the Octopus rotates in just one direction. When the clamp of the split seconds brake opens, the Octopus wheel has to rotate to its home position, which is done by the isolator wheel spring. Which means that it has to overcome the force of the split seconds brake spring.

So when approaching the isolator mechanism of the new 5204, Patek went back to the drawing board. And the first thing they did was get rid of the isolator wheel spring mounted on the split seconds wheel. Instead they ingeniously integrated this spring as part of the split seconds column wheel cap. The second thing they did was design an isolator that can move back and forth in two directions and thus doesn’t have to overcome the force of the brake spring which is much better for long term reliability.

Parts of the split-seconds mechanism on the 5402P
The unique Patek Philippe design is based on an isolator (A) controlled by the split-seconds column wheel (B). As soon as the split-seconds clamp (C) closes, the beak (P) of the isolator falls between two columns and with its teeth advances isolator wheel (D) that uncouples split-seconds lever. When the splitseconds clamp is opened again, the beak (P) of the isolator is lifted onto a column; its teeth turn the isolator wheel in the opposite direction and the split-seconds lever is released again. The swan’s neck cap of the column wheel doubles as a spring (F) that constantly presses the isolator (A) against the split-seconds column wheel.

Patek also redesigned the profile of the split seconds heart cam and return lever so that they nestle together in a much more secure home position eliminating the need used by the majority of split seconds chronographs of using a thicker chronograph seconds hand to mask the imprecise mating of these two hands.

The first model on the 5204’s maiden launch was a platinum case beauty with a silvered solid gold dial and luminous hands and indexes. To me this was a wink to the special order luminous 5004 watches owned by collectors such as John Mayer and Mike Ovitz. The dial of the 5204 is also distinguished by a moonphase indicator that opens across the lower half of the 6 o’clock subdial.

In 2017, Patek introduced a rose gold version also with luminous hands and indexes. Patek’s current catalogue shows three versions of the watch: a platinum watch with black dial, the rose gold watch with white dial and an incredible rose gold watch with black dial on the Patek 5-row grain of rice/bead bracelet.

Ref. 5204-1R

Ref. 5372 perpetual calendar monopusher split seconds chronograph: 2017 – Present day

• Platinum case with either blue or salmon dial.

Ref. 5372

In 2017, a full seven years after discontinuing its last Lemania 2310 based watches (the 5970 perpetual calendar chronograph and the 5004 perpetual calendar with split seconds chronograph) the brand launched a new reference 5372 perpetual calendar split seconds chronograph again based on the Lemania 2310 but this time with an all-new display for the calendar information and new configuration for the chronograph. The resulting timepiece is remarkably different from both the 5004 and the in-house based 5204. First, the watch is a monopusher chronograph with stop/start and reset activated by a sole rectangular button located at 2 o’clock. As the technical specifications of this watch from Patek states that it is CH 27 based, you can be certain that Patek’s signature Octopus-shaped isolater is used here to optimize the performance of this venerable movement’s split seconds function.

On the dial side the changes continue most noticeably with the moonphase indicator shifted to 12 o’clock and the day display integrated into the subdial at 9 o’clock and the month of the year located within the subdial at 3 o’clock. There is also a day/night indicator at 7:30 and a leap year indicator at 4:30.

What is particularly appealing about this timepiece is the 38.5mm case size which can be correctly considered as the perfect diameter for a modern classic with this complication. This magnificent decidedly retro-themed masterpiece comes in a platinum case with a blue dial or in a platinum case with a stunning salmon dial. Both iterations feature Arabic numerals. As of 2018 this watch is still in Patek’s catalog and seems to represent a kind of end-of-series for the mighty Lemania movement. This watch is rare enough that I’ve never seen one on a wrist in the wild.

Ref. 5372 Salmon dial

So this concludes my story on the incredible Stern family and their adventure throughout the 20th century and already well in the 21st century with the perpetual calendar chronograph, a complication that they not only invented but through sheer brilliance, are now synonymous with. I hope you enjoyed perusing as much as I enjoyed putting it together for you.