Différentiel d’Égalité

We’ll start off with the one that’s the new kid on the block, the Différentiel d’Égalité, which features Robert Greubel and Stephen Forsey’s 5th Invention.

Back in 2008, Greubel Forsey announced at Baselworld that they had come up with a way to provide the balance wheel with a steady rate of energy transfer from the mainspring, regardless of torque along the going train, using a spherical differential.

The way in which it achieved this constant energy dissipation, was by having a secondary spring on the differential, after the main spring, to regulate energy transfer. The secondary spring was able to rearm itself every five seconds, thereby, regulating and maintaining a constant rate of energy transfer. This was the Greubel Forsey 5th Invention.

The timepiece also features Greubel Forsey’s 30° inclined balance wheel that is fitted with a stopping mechanism for when you pull out the watch’s crown to adjust the time. The seconds indicators also reset themselves to zero when the crown is pulled out so that you are able to set time on the watch with better accuracy.

The Greubel Forsey Différentiel d’Égalité will be produced in a 44mm white gold case, limited to 33 pieces.

GMT Earth

Next the GMT Earth. Surely you are wondering, what makes the GMT Earth different from the Greubel Forsey GMT. This answer can be found on the back of the newer watch and has to everything to do with that 3D globe at 7 o’clock.

The rest of the GMT’s original functions remain intact with: hours and minutes; small seconds; 72-hour power reserve indicator; GMT time indicator and the 24-time zone universal time indicator visible through the caseback. The watch also retains its 24-second tourbillon reclined at 25°.

The Greubel Forsey GMT Earth will be produced in a 45.5mm white gold case, limited to 33 pieces.

Double Balancier

The last of the lot is one from SIHH 2016: The Double Balancier. Of course, when we first saw it, the watch was white gold and had a silvered gold dial. The 2018 version of the timepiece, now comes in a 43mm 5N red gold case and features a multi-layered gold dial in black, with engraved and oven-fired enamelled indexes. This, too, will be produced in a limited run of just 33 pieces.