Short answer

Caliber 863 is a manual-wind Omega chronograph with 17 jewels, a rhodium-plated finish, and a 21,600 vph beat rate. It sits on the Lemania 1873 base. Most watches sold as a fake "Speedmaster cal 863" use a Seagull ST19 movement or a real 861 with a re-stamped bridge. No mass-market factory makes a 1:1 copy of the Lemania 1873.

What caliber 863 is

  • Manual wind, no date, three-register chronograph
  • 17 jewels
  • 21,600 vph, 3 Hz
  • Power reserve: 46 to 48 hours
  • Rhodium-plated plates and bridges, plain grain
  • Bridge stamp: "863" and "17 JEWELS"

Omega used the 863 from about 1996 to 2003. It went into display-back Speedmasters only: ref 3572.50.00 with a hesalite front and sapphire back, and ref 3573.50.00 with sapphire front and back. The 1863 replaced it in 2003. The 1863 adds decorative striping on the bridges.

Fake movement tells

  1. Jewel count. The Seagull ST19 has 21 jewels. A bridge marked "21 JEWELS" with an 863 stamp is fake. So is a listing whose movement photo shows an ST19.
  2. Bridge shape. The ST19 descends from the Venus 175. Its balance cock and chronograph bridge outline differ from the Lemania 1873. Compare photos side by side.
  3. Engraving. Real 863 stamps are struck into the metal. Fakes use laser etch or paint. Look for white fill, shallow cuts, or type that runs into the bridge edge.
  4. Finish. The 863 plate is plain rhodium. Geneva stripes plus an "863" stamp is a mismatch.
  5. Caseback. The 863 shipped only in watches with a sapphire display back. A solid steel back plus an 863 claim fails.
  6. Movement number. An 863 carries an 8-digit number. Ask for a clear photo and check the digit count.

Price and listing checks

A used ref 3573.50.00 trades in the low four figures. Listings at $300 are not genuine. Ask for a 10x macro photo of the movement, the caseback stamp, and a video of the chronograph start, stop, and reset. Ask if the watch has a service record. A rebuilt 861 with new engraving will not have one.

What replicas get right

Modern replicas of the 3573.50.00 copy the case, dial, hands, and bezel. The movement is the weak point. Buyers who check the balance cock shape and the jewel count catch most of them.