Audemars Piguet has been producing calendar pocket watches from its founding in 1875. It did not make the first perpetual calendar wristwatch — that honour belongs to Patek Philippe which made the first perpetual calendar wristwatch in 1925, and the first perpetual calendar wristwatch in a series in 1941.

However, Audemars Piguet was the first to bring the leap year indicator to wristwatches – a feature formerly seen only in perpetual calendar pocket watches – with the ref. 5516.

Audemars Piguet ref. 5516 from 1950, without leap year indicator

Audemars Piguet’s own research has established that there were three examples of perpetual calendar wristwatches produced by the Vallée de Joux based brand at the start of 1950. All of these lacked a leap year indicator.

Now this was in a time when Audemars Piguet had yet to establish a reference numbering system with which they could track their collection of watches. By the time a system of reference numbers was established these three early 1950s perpetual calendar sans-leap year indicator were all designated ref. 5516.

We take it for granted today, but truth be told, a complicated calendar wristwatch that’s able to accurately track the months with 30 days versus 31 days and yet be able to differentiate the years when February has 28 days versus 29 days, but doesn’t have an indicator to tell whether it is or is not a leap year can’t prove to be quite confusing.

An image of the 5516 from Audemars Piguet's archives
Audemars Piguet yellow-gold perpetual calendar ref. 5516 from 1955 (Image © Revolution)
Movement used for the Audemars Piguet 5516

It wasn’t till in 1955 that Audemars Piguet produced its first series of perpetual calendar wristwatches with a leap year indicator. This was essentially an evolution of the earlier sans-leap year indicator ref. 5516 now updated with a leap year indicator, in 36.5mm cases.

There were only three pieces produced, all of which are said to have slight dial variations, but are all identifiable by their moon phase aperture at 12 o’clock and the 48-month subdial with leap year indication at 6 o’clock.

For greater legibility, the 48-month subdial was supplemented by a 12-month subdial at 3 o’clock that displays each month with greater clarity. These three watches were put into production in 1955 and delivered in 1959.

A 1957 version of the Audemars Piguet 5516 that was Tiffany signed

Subsequently, six additional ref. 5516 watches were put into production in 1957 and sold between 1963 and 1969, distinguished by their moon phase display at 6 o’clock, with leap-year subdials at 12 o’clock.

Audemars Piguet has recorded that three of the six watches initiated in 1957 are now part of the brand’s Heritage Department, one of which is even has a double signed, Tiffany dial.