A Greubel Forsey GMT Balancier Convexe GMT, In Titanium

One of Greubel Forsey’s most distinctive complications is the GMT complication, which the company handles in an unusual way. GF introduced the GMT complication in 2011, in a watch with a 24º inclined tourbillon, and with a three dimensional miniature planet Earth which rotates once every 24 hours. The watch has a 12 hour subdial for showing the time in a second time zone, but it also functions as a world timer – the globe is surrounded by a 24 hour ring, and on the back of the watch there is a rotating disk with reference cities, and two 24 hour inner and outer rings; the display is set up so that you can read standard time off the outer ring and Summer/DST off the inner ring, making it one of the few world time watches capable of accounting for local differences in the implementation of DST.

Greubel Forsey would go on to release several variations on its unique take on the GMT complication, including one with a quadruple tourbillon, but in 2022, it released the Balancier Convexe GMT, which it said would replace tourbillon-based versions of the GMT complication moving forward. The Balancier Convexe combines the Balancier concept, launched in 2017, which uses an inclined balance, with the same functionality of earlier GMT watches, and with a very large version of Greubel Forsey’s rotating globe.

The inclined balance offers the benefits of a tourbillon, but is less complex mechanically, and since there’s no tourbillon cage, the balance can be relatively larger. The inclination of the balance prevents the balance and balance spring from assuming either a completely flat or completely vertical position except very briefly, and since the most extreme positions are avoided, positional errors are reduced. Local time is read off the larger 12 hour subdial that surrounds the rotating Earth; the time in different time zones around the world can be read off the day/night 24 hour disk, and the time in a second time zone can be read off the smaller 12 hour subdial to the right of the Earth display. Running seconds are visible in the subdial at 5:00.

The watch is relatively large, at 46.50mm measured at the bezel, and 13.75mm thick measured at the case, and 17.4mm including the sapphire crystals. Despite the size, the watch is relatively light thanks to its all titanium construction, and the sharp downward curvature of the lugs makes it more wearable than you would think from the dimensions alone. As you’d expect from Greubel Forsey, the level of finish is impressive and quality is immaculate, with polished and beveled steelwork and sharp inner transitions where appropriate, including at the inner and outer ends of the rounded balance bridge, and on the cock for driving wheel for the small seconds. The balance is free-sprung, with an overcoil balance spring whose outer terminal curve is held in place with a meticulously polished and beveled stud carrier.

One of the basic problems with most world time displays, is that they don’t account for locations which observe Summer/Daylight saving time. Implementing a world time complication which does so can be done, although with a significant increase in mechanical complexity (one ingenious example is the Bovet Récital 28 Prowess 1). Greubel Forsey has come up with an interesting and easy to use solution.

On the back of the watch is a second world time display, which offers a more abstract but more precise world time indication and which allows you to easily read the correct time in locations where Summer Time is observed. Standard time is read off the outer 24 hour ring; in New York, the current time shown is about 8:30 AM. If you check the position of New York against the inner 24 hour ring (labeled Summer Time) which is an hour ahead of the outer ring, you can see that the time shown is 9:30, which would be the correct local time if accounting for Summer Time. Locations where Summer Time rules are observed are shown against a white background, and locations for which Summer Time is not observed, are shown with white letters against a black background.

World time complications using the classic design developed in the 1930s by Louis Cottier have a particular beauty and elegance, but Greubel Forsey’s take has an overt poetic charm unique to it, with the rotating miniature Earth providing a direct experience of the phenomenon of time passing as the Earth rotates, and the ability to account for locations that observe Summer Time is icing on the cake. One of the beauties of the system is that you can still read standard time for a given time zone, if you’re in a location where Summer Time is not observed. New York is GMT-5, but so are Panama, Peru, Ecuador, and Columbia, all of which are on standard time all year ’round (which I wish we would emulate – I’m not a fan of Summer Time/DST, which has provable connections with a higher mortality rate from heart attacks and traffic accidents, among other things).

It’s a fascinating watch in its conception and in its execution. I’ve worn earlier, tourbillon versions of Greubel Forsey’s GMT complication on two occasions for reviews and there is something rather hypnotic about the rotating Earth – it’s an interesting experience to look at it and locate yourself on the globe in your imagination, and think about the fact that the Earth under your feet is rotating at the same speed as the Earth on your wrist. The GMT complications from Greubel Forsey are among my favorite watches from the company; they have technical sophistication, physical beauty, and care in execution, and offer not only a different perspective on the world time complication, but also a healthy dose of philosophical perspective as well.

For more information on the Greubel Forsey Balancier Convexe GMT, contact The 1916 Company.