Answer first
A counterfeit Omega Seamaster 300M offered as a "291" fails on records before it fails on looks. The 291 in those listings is a seller code or a vintage case reference, not a standard Seamaster 300M reference number, so the paperwork and the caseback stamp are where the inspection starts. If the reference, the serial, and the movement do not agree, stop and walk away.
Prerequisites
- Bright, diffused light and a 10x loupe
- Digital calipers for case and bracelet measurements
- Clear photos of the caseback, lugs, clasp, and movement
- A watchmaker willing to open the case and document what is inside
Step-by-step checks
- Ask the seller for the full reference number and the serial from the caseback and from the movement. Write both down.
- Compare the reference against Omega's published catalog for the Seamaster 300M line. A number that resolves to a different model, a different case size, or nothing at all is a mismatch.
- Check the caseback engraving under the loupe. Genuine stamping has crisp edges, consistent depth, and a hippocampus with defined scales and trident. Fake stamping looks shallow, soft, or laser-etched.
- Measure the case with calipers. Diameter, thickness, and lug width should match the published specs for the reference to within a few hundredths of a millimeter.
- Rotate the bezel. A genuine 300M bezel moves in 60 defined clicks, one direction only, with no back play and no grinding. A pip that sits off-center at 12 o'clock is a fail.
- Inspect the dial print under the loupe. Applied indices sit in metal frames with level lume fill, the Seamaster script has clean stroke contrast, and the date window sits square with the correct magnification.
- Compare the hands. Hour, minute, and second hands have specific proportions and finishes per generation, and the lume plots align with the dial markers.
- Test the crown and helium escape valve. Threads engage with light pressure, the logo relief is sharp, and the valve seats flush with the case.
- Examine the bracelet and clasp. End links fit the lugs with no gap, screws have the correct head profile, and clasp stamping has depth rather than surface etching.
- Have the watchmaker open the case. Read the rotor engraving, the balance type, the escapement, and the movement serial. Compare the movement serial to the paperwork.
- Match the box, warranty card, and serial continuity. Numbers that do not line up across the three documents end the deal.
Where fakes give themselves away
Modern replica cases copy outside dimensions well, so the movement is the reliable tell. Genuine Seamaster 300M watches use Omega's co-axial calibers with a free-sprung balance and specific bridge geometry. Counterfeits carry decorated clones of ETA or Asian movements with a stamped plate over the top, and the engraving on that plate is thinner and shallower than factory work. A watchmaker with the caseback off settles the question in under five minutes.
Dial and crystal details
Look at the anti-reflective coating on both faces of the sapphire. Genuine coating produces a faint blue or purple cast at an angle and keeps the dial readable in direct light. Fakes often coat one side or skip the coating, and the dial washes out. Check the date disc font and the alignment of the printed indices with the applied markers.
omega seamaster 300m 291 counterfeit
Bezel insert and lume
The ceramic insert on a genuine watch has a matte, even surface with a recessed lume pip set under a sapphire cap. Fake inserts show gloss, uneven pigment, or a painted pip. Charge the lume with a phone light and watch the decay. Genuine lume glows bright and fades over hours; counterfeit lume fades in minutes.
Paperwork and price
A price well below the market for the stated reference is the oldest signal there is. Ask for the original purchase receipt, the warranty card with the AD stamp, and the serial on the card. Call the brand's service center with the serial and ask them to confirm the model it belongs to. A seller who refuses an in-person inspection by a watchmaker is telling you what you need to know.
Before you pay
- Get the serial and reference in writing.
- Book a watchmaker inspection with the case opened.
- Request a written appraisal that names the model and the movement.
- Pay through a method with a dispute process, never by wire.