he new GMT Balancier Convexe replaces its predecessor entirely – not as a variation, but as a complete reinterpretation. With a redesigned case, an integrated power reserve, and enhanced ergonomics, it becomes the purest expression of Greubel Forsey’s GMT complication to date – and the only GMT model in their current collection.

This new creation preserves the iconic theatrical architecture of the original GMT Balancier Convexe, while refining its proportions and mechanical layout. The Convexe case, still sculpted in titanium, is now more compact at 42.90 mm at the caseband for improved wearability. A new 72-hour power reserve indicator is seamlessly integrated into the dial, bringing added functionality without disrupting the visual harmony.

The movement now contains 496 components, 73 more than its predecessor, attesting to a re-engineering of the calibre to accommodate new displays and improved chronometric performance. Finishing remains uncompromising: the inclined escapement is suspended beneath a flat black polished and barrel polished steel bridge, resting on polished steel pillars. The Terrestrial globe – one of the Atelier’s most emblematic elements – remains, rotating in real time within a layered amphitheatre of time indications.

On the caseback, a sapphire disc engraved with 24 cities reflects both universal time and summer/winter time, with La Chaux-de-Fonds replacing Paris – a subtle but meaningful shift.

This new GMT Balancier Convexe will be made in a strictly limited series of 22 timepieces.

TECHNICAL SPECIFICATIONS

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 • power-reserve

MOVEMENT

• MOVEMENT DIMENSIONS
  • Overall diameter: 37.80mm
  • Thickness: 13.80mm
• NUMBER OF PARTS
  • Movement: 496 parts
  • Escapement platform: 59 parts
• NUMBER OF JEWELS
  • 72
  • Olived-domed jewels in gold chatons
• CHRONOMETRIC POWER RESERVE
  • 72 hours
• BARRELS
  • Two series-coupled fast-rotating barrels (1 turn in 3.2 hours), one of which is equipped with a slipping spring to avoid excess tension
• 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 and nickel-silver
  • Frosted, polished bevelling and countersinks, straight-grained flanks
• ESCAPEMENT PLATFORM
  • Inclined at a 30° angle
  • Flat black polished steel, polished bevelling and countersinks, straight-grained 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
• 72-hours power reserve on a sector

EXTERIOR

CASE
• Titanium with curved sapphire crystal
• Three-dimensional, variable geometry-shaped bezel, hand-polished with hand-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: 42.90mm
• Bezel diameter: 44.90mm
• Case height: 15.10mm
• Height on synthetic sapphire crystals: 17.60mm

WATER RESISTANCE OF THE CASE
• Water-resistant 5atm - 50m – 164ft (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, red triangles with Super-LumiNova
• 2nd time zone GMT indicator, red triangle
• Small seconds in polished blued steel, flat black polished head

STRAP AND CLASP
• Hand-sewn textured rubber or 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