Greubel Forsey places the Earth back at the centre of its universe with the extraordinary GMT Balancier Convexe.
This new GMT calibre replaces all previous GMT models and features, for the first time, its signature inclined balance wheel, as if in orbit around the Earth. A construction whose aesthetic architecture is matched only by its technical mastery and which confirms Greubel Forsey’s resolutely contemporary approach to Fine Watchmaking.
The perfect titanium sphere with its continents, seas and oceans, is one of the Atelier’s most emblematic creations. It was the centrepiece of the GMT, GMT Earth, GMT Quadruple Tourbillon and GMT Sport, some of Greubel Forsey’s greatest successes to date. Greubel Forsey is dedicating a brand new calibre to the Terrestrial globe, decisively replacing its predecessors.
The Earth is flush with the sapphire crystal, almost close enough to the surface to touch, it moves in a constant 24-hour rotation, just as the Earth rotates in real life. This amphitheatre is bordered by three rings which indicate two complementary times: hours and minutes local time, as well as universal time.
The 24 time zones displaying universal time are set against a black background if the time indicated is at night, and on a white background during the day time.
Local time is indicated on the two outer rings: one for the hours on a grey satin-finished ring, and minutes on a thin black outer ring. Each time indication has its own hand with a red triangular tip filled with luminescent material. These hands move on two further rings, engraved with key words dear to the Atelier, to display GMT.
For the caseback of the timepiece, Greubel Forsey opted to keep the disc with 24 time zones indicating the UTC time of the 24 reference cities, but with a rather appropriate modification: the UTC of Paris has been replaced by the city where Greubel Forsey has been established since its early days: La Chaux-de-Fonds, Switzerland.
The beating heart of the timepiece, appreciated by collectors for its remarkable chronometric performance, is a spectacular sight. The 30° inclined balance wheel, seemingly suspended in mid-air, is held by a beautiful flat black polished and barrel polished steel balance wheel bridge on polished steel pillars. To its right, the small seconds, displayed with a blue gold hand completes the ensemble.
Finally, the inside of the case is polished so that it mirrors the escapement platform, the Terrestrial globe, and nearly every element visible on the dial side, thus adding incredible depth to this new construction.
The convex case, made of titanium and with a diameter of 46.5mm around the bezel and 43.5mm around the caseband, it hugs the curve of the wrist perfectly. It also represents the major technical feat of achieving a movement that follows an imperceptible slope of just a few degrees.
Greubel Forsey will only make 66 GMT Balancier Convexe timepieces: 22 per year between 2022 and 2024.
Technical Specifications:
GMT Balancier Convexe
In titanium
Limited edition
Patented hand-wound movement
GMT • 2nd time zone • rotating globe with universal time and day-and-night • universal time on 24 time zones • summer and winter time • cities observing summer time • GMT pusher • 30° inclined Greubel Forsey balance wheel system • hours and minutes • small seconds
Movement
Movement dimensions
• Overall diameter: 38.80mm
• Thickness: 13.41mm
Number of parts
• Movement: 423 parts
• Escapement platform: 59 parts
Number of jewels
• 42
• Olived-domed jewels in gold chatons
Chronometric power reserve
• 72 hours
Barrels
• Two coaxial series-coupled fast-rotating barrels (1 turn in 3.2 hours), equipped with a fixed mainspring-bridle
Balance wheel
• In-house variable-inertia with 6 gold mean-time screws (12.60mm diameter)
Frequency
• 21’600 vibrations/hour
Balance spring
• Phillips terminal curve
• Geneva-style stud
Bridges and main plates
• Titanium
• Frosted, polished bevelling and countersinks, straight-grained flanks
Escapement platform
• Inclined at a 30° angle
• Flat black polished steel, polished bevelling and countersinks, straightgrained flanks
• Polished steel pillars
• Flat black polished and barrel polished steel balance wheel bridge
Gearing
• Involute circle profile
• Inclined gear with profiled teeth on fourth wheel
Displays
• Hours and minutes
• Small seconds
• 2nd time zone GMT
• Rotating globe with universal time
• Day-and-night
• 24 time zones universal time
• Summer time, winter time
Exterior
Case
• Titanium with curved sapphire crystal
• Three-dimensional, variable geometry-shaped bezel, hand-polished withhand-finished straight graining
• Profiled lugs, screwed fixing
• Transparent back with curved and high domed synthetic sapphire crystal
• Engraved GMT pusher
• Titanium security screws
• Raised engraving “GMT” and “Greubel Forsey”
Case dimensions
• Caseband diameter: 43.50mm
• Bezel diameter: 46.50mm
• Case height: 13.75mm
• Height on synthetic sapphire crystals: 17.40mm
Water resistance of the case
• Water-resistant 10atm – 100 m – 328ft (standard NIHS 92-20/SN ISO 22810:2010)
Crown
• Titanium, polished, frosted and straight-grained, with GF logo
Dial side
• Terrestrial globe in titanium, relief-engraved continents, ocean blue treatment
• Day-and-night UTC indicator in titanium, engraved and lacquered
• GMT indicator in gold
• Amphitheatre hour-ring with engraved and lacquered minute-circle
• Small seconds indicator in gold
Movement side
• Synthetic sapphire disc displaying city names surrounded by 2 rings (UTC and summer time) engraved and lacquered, hand matt lapped
• Gold “summer time” plate with limitation number, raised engraving, hand matt lapped
Hands
• Hours and minutes with Super-LumiNova, red triangles
• 2nd time zone GMT indicator, blue triangle
• Small seconds in polished blued steel, flat black polished head
Strap and clasp
• Non-animal material, rubber with text in relief, titanium folding clasp, engraved GF logo
• On demand: 3-row metal bracelet in titanium, folding clasp with integrated fine adjustment, engraved GF logo
Price on application
For more information please visit Greubel Forsey