Short answer

Omega never made a caliber 321 co-axial. Caliber 321 is a manual-wind chronograph from 1957. The co-axial escapement is a separate design that Omega used in automatic movements from 1999. A listing that names both is naming two movements at once. Before you pay, check the movement name, the beat rate, and the caseback.

The two movements

  • Caliber 321: manual wind, column wheel, 18,000 vph (2.5 Hz), 17 jewels, released in 1957 in the Speedmaster. Based on the Lemania 2310. Discontinued around 1968. Omega brought back a caliber 321 in 2019. That version is still manual wind and still not co-axial.
  • Co-axial: an escapement designed by George Daniels. Omega adopted it in 1999. The first co-axial caliber was the 2500, an automatic. Later co-axial calibers include the 8500, 9300 and 9900.

Beat rate is the quick check

A timegrapher or a slow-motion phone video of the balance wheel shows the rate. Caliber 321: 18,000 vph, which is 5 beats per second. Co-axial 2500: 25,200 vph, which is 7 beats per second. Caliber 1861: 21,600 vph, which is 6 beats per second. A watch that reads 28,800 vph is not a 321 and is not a 2500.

What replica listings contain

Most low-cost Speedmaster-style replicas run a Seagull ST19. That is a Chinese manual-wind column wheel chronograph at 21,600 vph. Automatic pieces sold as co-axial run a copy of the ETA 2824 or a DG2813, at 21,600 or 28,800 vph. Neither is a 321. Neither has a co-axial escapement. Other tells: sub-dial positions at 3, 6 and 9 against other layouts, pusher travel, chronograph reset snap, dial print quality, and caseback engraving depth.

US legal position

Counterfeit goods that carry a registered trademark are barred from import. 18 U.S.C. 2320 covers trafficking in counterfeit goods. CBP seizes shipments under 19 CFR Part 133. Personal use is not an exception. A seized parcel is not returned, and the seller does not refund it.

Checks before money changes hands

  1. Ask for the movement name and the beat rate in writing.
  2. Ask for a timegrapher photo or a 10-second video of the balance wheel.
  3. Ask for a caseback photo. The 321 Speedmaster has a solid caseback.
  4. Ask which reference number the watch copies.
  5. Ask for the return terms in writing.