Short answer

The 210 in an Omega reference number marks the Seamaster Diver 300M family. A reference such as 210.30.42.20.03.001 is a 42 mm stainless steel Seamaster Diver 300M with a blue dial. Omega does not publish a full public decoder for every digit group, so later groups change with dial color, bracelet, and market. The 210 prefix is the part that stays the same across the line.

Genuine specs on a 210 reference

The 210.30.42.20.03.001 uses a 42 mm steel case, a 20 mm lug width, and a thickness near 13.6 mm. Water resistance is 300 m. The bezel is blue ceramic with a white enamel dive scale. The dial is blue ceramic with laser-engraved waves. A helium escape valve sits at 10 o'clock.

Inside is the Omega Co-Axial Master Chronometer Calibre 8800. It runs at 25,200 vibrations per hour, holds 55 hours of power reserve, and resists magnetic fields to 15,000 gauss. METAS certifies each movement. US list price sits near $6,000 and moves with Omega's annual increases.

How replicas of this model differ

  • Beat rate. The 8800 runs at 25,200 vph, which is 7 beats per second. Many replica movements run at 21,600 vph, or 6 beats per second. The sweep of the second hand looks different.
  • Helium escape valve. The genuine valve opens and seals. On replicas it is often a fixed crown.
  • Dial waves. Genuine waves are laser-engraved into the ceramic. Replica waves are stamped or printed, with softer edges and a different depth.
  • Caseback. Genuine has a sapphire back with a wave edge and the hippocampus. Replica engraving is shallow.
  • Lume. Genuine uses Super-LumiNova. Replica lume dims faster.
  • Bracelet. Genuine end links meet the case with no gap. Replicas show gaps and sharp edges.

Legal status in the United States

Selling counterfeit watches is a federal crime under 18 U.S.C. 2320. A first offense by an individual carries up to 10 years in prison and a $2,000,000 fine. Under 19 U.S.C. 1526, US Customs and Border Protection can seize and destroy counterfeit goods at import. A single watch bought for personal use faces seizure, not resale. Counterfeits carry no Omega warranty and no service from Omega's network.

What to check on any 210 reference

Ask for the reference number on the caseback, the movement number, and the METAS certificate card. Omega can verify a serial number through an authorized dealer or a service center. Genuine 210 references hold resale value. Counterfeits do not.