From The Tourbillon To World Time: Greubel Forsey Presents The GMT

The ”GMT” marks a significant milestone for Greubel Forsey, as it is the brand’s first timepiece to feature a complication other than a tourbillon. The GMT is distinguished by an eye-catching rotating globe offering an intuitive view of the time all over the world, as well as a 24 Seconds Tourbillon.

With this remarkable timepiece, Robert Greubel and Stephen Forsey have focused their energy on indicating a second time zone, a complication traditionally denoted by GMT (Greenwich Mean Time), the historical reference meridian for navigators. The GMT features a wonderful, three-dimensional temporal representation: A rotating terrestrial globe offering a truly original view of time all over the world. This technical yet poetic marvel provides us with a completely new way of perceiving the different time zones.

Nestled in a prominent position at 8 o’clock, the ‘flying’ globe is ingeniously secured at just one end of its rotational axis – the South Pole – allowing for optimal views of the intricate surface that has been crafted on the strong, yet lightweight, titanium sphere. While the globe makes one complete rotation every 24 hours anticlockwise – the Earth’s natural rotational direction – the position of the continents can be neatly cross-referenced with the 24-hour, day-and-night indicator on the equatorial chapter ring.

The night-time hemisphere – 18:00 to 6:00 – is indicated by a blackened half of the ring around the globe, while the daytime hemisphere – 6:00 to 18:00 – is indicated by a whitened portion. The latter is superbly enhanced by a lateral window cleverly integrated into the caseband, which lets in light to symbolise daytime on the globe, and reveals more of the southern hemisphere.

The intuitively interpreted globe is complemented at 10 o’clock by the 12-hour second time zone dial giving a precise indication of the time in a designated second country or city and is easily adjusted using the quick-set, dual-function pusher on the caseband at 10 o’clock.

Cascading clockwise around the dial-side are the main indications comprising a principal hour-minute dial at 1 o’clock, on top of which is a small seconds dial at 2 o’clock, while at 3 o’clock is a sectorial power reserve indicator.

The specially developed movement of the GMT features the 25° inclined Tourbillon 24 Secondes cage, one of Greubel Forsey’s major patented inventions. In addition to its superb chronometric virtues and reliability, its compact size allows space for the other complications.

Spatially, the combination of elements on the dial-side is perfectly balanced, with a striking sense of depth offered by the globe and by the Tourbillon 24 Secondes at 5 o’clock which together form a triple asymmetry giving rise to a controlled tension that plays subtly with the circularity of the case, while never totally rupturing it.

Turning over the GMT reveals the beautifully crafted ‘worldtime’ disc bearing the names of 24 cities each representing one of the different global time zones. Aligning the relevant city with the local hour on the outer chapter ring – or inner ring for cities with summer time – sets the dial-side globe in the correct position.

On the technical side, the movement consists of 436 components, 87 of which are used in the tourbillon cage, which weighs in at just 0.36 grams. Two coaxial mainspring barrels connected in series provide a power reserve of 72 hours and the movement is equipped with a variable inertia balance beating at 21,600vph/3Hz and a Phillips terminal curve balance spring.

Plates and bridges are hand-finished, frosted, spotted, bevelled, straight-grained, matt lapped and flat black polished. The dial is in 18k gold and the whole movement is housed in a white gold case of 43.50mm in diameter with a height of 16.14mm. The case is completed by domed sapphire crystals for the dial-side, display-back and lateral window, all treated with anti- reflective coating. The timepiece is complemented by a hand-sewn black alligator leather strap with a Greubel Forsey folding clasp in white gold.

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Source: Ildico Inc