Answer

A fake Omega Seamaster 300M fails on the caseback, movement, and bezel. Genuine current models use Omega Master Chronometer movements. The caseback has a seahorse. The reference number and serial sit on the case or lugs. Fakes often use a flat caseback, a sticker, or a wrong reference number. The bezel on a real Seamaster 300M turns with 120 clicks. A fake bezel can have 60 clicks or no clicks.

Check the caseback and serial

Omega stamps the reference number and serial on the case or lugs. For a Seamaster 300M, reference numbers start with 210.30, 210.32, or 210.92. The serial is 8 digits. Fakes often show a serial that repeats on many watches. Fakes also use laser etching that sits above the surface. Genuine engraving cuts into the metal.

Check the movement

The real Seamaster 300M uses Omega calibre 8800 or 8900. These movements have a Co-Axial escapement and a Master Chronometer certification. A fake uses a low-grade automatic or quartz movement. The rotor on a fake may spin with noise. The real rotor spins with little sound. The real balance wheel beats at 25,200 vibrations per hour. A fake often beats at 21,600 or 28,800. A watchmaker can open the caseback and read the movement number.

Check the bezel and dial

The bezel insert on a real Seamaster 300M is ceramic. The numbers and markers are engraved and filled with enamel. The bezel turns with 120 clicks. The action is tight. A fake bezel uses printed paint. The bezel can turn with 60 clicks or no clicks. The dial on a real watch has applied markers. The lume is white or vintage. The date window sits at 6 o'clock on current models. A fake dial may have a date window at 3 o'clock. The wave pattern on the dial is laser cut on real models. Fakes use a stamped pattern.

Check the crown and helium valve

The Seamaster 300M has a crown at 3 o'clock. It also has a helium escape valve at 10 o'clock. The valve on a real watch is a separate screw-down part. A fake may glue a fake valve or leave it off. The crown on a real watch has a signed Omega logo. The crown screws down. A fake crown may not screw down. The crown guards on a real watch are part of the case. Fakes often have sharp edges.

Check the bracelet and clasp

The real bracelet has screws in the links. The clasp has a stamped Omega logo and a diver extension. The clasp code matches the reference. A fake bracelet uses pins and split pins. The clasp logo is stamped or engraved. The fake clasp can feel light. The real clasp has a micro-adjust function on some models. The end links on a real watch fit flush to the case. Fakes often leave a gap.

Use paperwork and tools

A real Seamaster 300M comes with a warranty card. The card has a magnetic strip and a pictogram. The card matches the serial and reference. A fake card is often blank or has a wrong date. A watchmaker can verify the movement and case. An Omega boutique can check the serial in the Omega database. No online guide replaces a hands-on check.