As is usual for Greubel Forsey, this watch is different, and it is so packed with information that the circular dial has a few bulges here and there, as if the sheer pressure of innovation had expanded the case. The GMT function is particularly useful for travellers, and for people with contacts in other countries, because, knowing the time in your correspondents’ location, you can phone them without fear of waking them up. Usually, a GMT watch simply has a second 24-hour scale or subdial, with an extra hand, indicating the time in the second time zone. With their own GMT watch, Robert Greubel and Stephen Forsey have gone much further. The watch has a model of the earth in a housing on the bottom left of the case, made in titanium. It rotates exactly like the Earth, anticlockwise, making one rotation every 24 hours. A scale around the globe has a dark sector from 6 o’clock in the evening to 6 in the morning, and a light sector corresponding to daytime hours. At first glance, the orientation of this scale seems rather illogical, but then you discover that Greubel and Forsey have added a neat detail. A window on the caseband lets daylight into the case, illuminating the half of the globe corresponding to the daytime hours. So at a glance you can get an idea of the parts of the Earth that are in their night-time hours, and which are basking in the sun.
Above the rotating globe, there is a more conventional subdial for a second time zone, which can be set using the GMT button next to it, on the caseband. The other indications on the dial are relatively straightforward: hours and minutes on the largest dial at top right, which has a small seconds dial superimposed onto it. Under this is the power reserve indicator. At the bottom of the dial, the 24 Secondes tourbillon is inclined at 25°. Its unusually fast speed – 24 seconds for a complete rotation, instead of the usual 60 seconds or more – improves precision.
There is even more on the caseback. The world-time disc has 24 cities marked on it, one for each time zone. Pressing the GMT button rotates the disc with the cities, so that the local time for the desired city can be set. A second, inner chapter ring is marked with Summer Time hours, thus creating the attractive spiral arrangement of the city names. A golden sun is placed at midday, again for a more intuitive view.
Finish is of course at the highest level. 87 of the total of 436 components are used for the tourbillon cage, which unbelievably weighs just 0.36 grams. The two mainspring barrels provide a power reserve of 72 hours. It is a large watch at 43.5 mm diameter, with a height of 16 mm. The case is in red or white gold; it has a black alligator strap with a folding clasp.