Answer first
Omega builds the Constellation Globemaster at 39 mm. The Omega catalog has no 40 mm Globemaster. Sellers write "40mm" for two reasons: they round 39.4 mm up, or they measure the case with the crown included. A smaller group of replicas uses a generic 40 mm case that does not match the original profile. Ask for caliper photos of the case at the bezel, crown excluded, before you pay.
What the genuine watch measures
The steel Globemaster uses Calibre 8900: 60 hours of power reserve, 25,200 vph, Co-Axial escapement, Master Chronometer certification from METAS. Gold cases use Calibre 8901 with a gold rotor. The movement holds rate in magnetic fields up to 15,000 gauss. The dial is a pie-pan shape, with faceted indices and a date window at 3 o'clock. The bezel is fluted. The Annual Calendar version measures 41 mm, not 40 mm, and runs a different movement.
Why listings say 40mm
Case width on a finished watch depends on where you put the calipers. Omega quotes 39 mm. Most sellers quote the widest point, which reads 39.3 mm to 39.6 mm on a steel case. Some add the crown, which pushes the number past 40 mm. Listings that show a 40 mm body come from unbranded case suppliers, and those cases have thicker lugs and a taller profile than the original.
Movements inside replicas
Three movement types appear in Globemaster replicas. The Seagull ST2130 is a clone of the ETA 2824 and runs at 28,800 vph. The Miyota 9015 runs at 28,800 vph with about 42 hours of reserve. The third type is a decorated automatic with a plate stamped "8900" and a fake balance cock. The 28,800 vph rate is the tell: the real 8900 runs at 25,200 vph. A timegrapher shows the gap in one reading. No replica carries METAS certification, and none holds rate near a 15,000 gauss field.
Points to inspect
- Case width at the bezel: 39 mm, crown excluded.
- Bezel flutes: deep cuts with clean polish. Shallow cuts on cheap builds.
- Pie-pan dial: the outer ring slopes down toward the center. A flat dial is wrong.
- Date window at 3 o'clock: framed, centered, correct font.
- Crystal: sapphire with anti-reflective coating on both faces.
- Caseback engraving and medallion: compare to brand photos of the exact reference.
- Bracelet end links: no gaps at the lugs, no rattle at the clasp.
Prices and availability
Globemaster replica listings run from about $180 to $500. The model is low volume next to the Seamaster 300M and the Speedmaster, so fewer sellers stock it. Factory labels change often; sellers reuse names such as ORF, VSF and JHF on the same catalog photos. Ask for dated photos of the unit in stock. Wire and crypto payments remove buyer protection, and chargebacks are not available.
Legal note
Counterfeit watches are illegal to import into the United States. U.S. Customs and Border Protection can seize a shipment and destroy it. The buyer gets no refund and no recourse.