Quick answer

A counterfeit Omega Seamaster Diver 300M copies the case shape and the dial print. It does not copy the movement, the caseback, or the pressure rating. A listing that reads 30 m instead of 300 m or 30 bar shows the gap at once. The genuine watch has a 300 m rating, a helium escape valve at 10 o'clock, and a METAS Master Chronometer certificate.

What the numbers mean

Genuine Seamaster Diver 300M casebacks are marked 300 m / 1000 ft and 30 bar. The 30 bar figure equals 300 m of static pressure. A 30 m marking is a different claim. Under ISO 22810, 30 m means splash and rain resistance, not swimming. Under ISO 6425, a diver's watch must be rated to 100 m or deeper and pass overpressure, condensation, and thermal shock tests.

Why a 30 m fake fails in water

Seals on a 30 m case are built for light contact with water. A gasket set that meets a 30 m claim leaks at pool depth. Salt water and chlorine reach the movement and rust the steel parts.

Movement and caseback

Seamaster 300M models from 2018 use Omega calibre 8800. The movement has a Co-Axial escapement, a silicon balance spring, 15,000 gauss magnetic resistance, and a 55 hour power reserve. It sits under a sapphire caseback, so the owner sees the rotor and the bridges. Most fakes use a Miyota 8215 or a copy of an ETA 2824 and hide it behind solid steel.

Checks in the hand

• Helium escape valve: sits at 10 o'clock on the real watch, with a crown that unscrews. Fakes omit it or fit a fixed stud.
• Bezel: ceramic insert, filled numerals, 120 clicks, no backplay. Fake bezels rock and the paint wears off.
• Dial: laser cut waves with sharp edges. Fakes print the waves flat. The date window sits at 6 o'clock with a metal frame.
• Lume: blue Super-LumiNova on hands and markers. Most fakes glow green and fade in minutes.
• Finish: brushed and polished surfaces meet at straight lines. Fake lugs show rounded edges and tool marks.

Papers and serials

Omega engraves the serial on the case and repeats it on the movement. A mismatch points to a swapped part. Real kits include a Master Chronometer card with the METAS test result and a numbered certificate. Counterfeit cards exist, so the serial check carries more weight than the paperwork.

Legal status in the United States

Counterfeit goods that carry a trademarked name are illegal to import. U.S. Customs and Border Protection can seize the shipment, and the buyer can face a civil penalty. Omega registers the Seamaster name and the wave dial.

Bottom line

Read the caseback first. 300 m and 30 bar are correct. 30 m is not. Then check for the helium valve, the sapphire caseback, and the calibre 8800 rotor. If the back is solid steel, the watch is not a Seamaster Diver 300M.