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In-house manufacture caliber · caliber Greubel Forsey GMT Sport (in-house, hand-finished)
Large case: suits wrists 7 in+ (18 cm+)
45 mm case. A bold, statement-size wear. Best suited to larger wrists where the case sits flush.

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Authentication

Verify the GMT disc advances at the correct rate; any Sport colorway not in Greubel Forsey official catalogues is non-genuine.

Known issues in the market
  • Sports colorways not documented in official catalogues are non-genuine configurations.
  • The GMT disc must turn at the correct 24-hour rate.
AreaWhat to checkWhat is correctRed flag
dialGMT disc rotation rateGMT disc advances at correct 24-hour rateGMT disc stationary or advancing at incorrect rate; mechanism fault
dialColorway verification against catalogueColorway documented in official Greubel Forsey GMT Sport catalogueColorway not in official catalogues; non-genuine configuration
movementHand-finishing standardAll components hand-finished to Greubel Forsey standardMachine-finished components; non-genuine or modified movement
Common legitimate replacements
  • No service-compatible replacements; Greubel Forsey service only.
Expert resources: Greubel Forsey direct; official press releases for colorway verification.

Authentication guide

Last reviewed June 2026

The GMT Sport is Greubel Forsey's most accessible piece and the only one with an integrated bracelet option. It still contains a hand-finished inclined tourbillon. Replica risk is effectively zero; condition and provenance are the evaluation axes.

Known reproduction risks

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LOW

No credible mechanical reproduction of any Greubel Forsey exists.

  • Non-inclined tourbillon cage (flat mounting)
  • Machine marks under loupe replacing the hand-finishing

Greubel Forsey's finishing standards and production volume make mechanical reproduction effectively impossible at this time. The primary risk is provenance misrepresentation on a genuine piece.

Dial variants by era

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EraDescriptionIdentifiers
2019 to presentMulti-layer dial with inclined tourbillon visible at 5 o'clock; 24-hour GMT display on a subsidiary dial; power reserve indicator; titanium case with integrated metal bracelet or rubber strap.
  • Tourbillon cage is inclined at 30 degrees to the movement plate; this angle is visible and deliberate; the cage presents at a tilt relative to the dial plane
  • 24-hour GMT disc or hand is separately readable for a second time zone
  • Power reserve display shows the stated reserve for the caliber
  • Case back reveals at least three distinct movement planes due to the depth of the movement architecture

Service part flags

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Inclined tourbillon

Original: Tourbillon cage inclined at 30 degrees to the movement plate; the inclination is the Greubel Forsey house signature across all tourbillon models.

Replacement tells
  • Tourbillon cage mounted flat (parallel to the dial plane): not a Greubel Forsey inclined tourbillon
  • Tourbillon cage absent
Movement finishing

Original: All surfaces hand-finished to extreme standards; under loupe, every bridge shows a combination of polished bevels, circular graining, and hand-applied Geneva stripes; no machine marks on any surface.

Replacement tells
  • Machine marks under 5x loupe on any bridge
  • Bevels not mirror-polished
  • Absence of hand-applied Geneva stripe pattern on movement plates

Case back markings

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2019 to present
  • Sapphire caseback showing the full movement depth across three planes
  • "GREUBEL FORSEY" on the movement plate
  • Titanium case back ring with reference and serial
  • Serial number within the expected production range for 2019 to present (total production approximately 100 to 150 watches per year across all Greubel Forsey references)

Movement tells

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  • The inclined tourbillon cage completes one rotation per minute; time it for 60 seconds to confirm.
  • The GMT disc or hand should track 24-hour time independently of the main time display and be settable without stopping the movement.
  • Through the caseback, the movement occupies the full case depth with visible differential architecture between the tourbillon and GMT complications.
  • At this production volume, serial numbers should correlate to documented production records. Greubel Forsey maintains detailed records and can confirm any serial number.
Sources: Greubel Forsey official authentication; Hodinkee Greubel Forsey GMT Sport feature.

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