Short answer

A fake Omega caliber 1861 is not a copied Omega movement. It is a different movement inside a watch that a seller labels as an 1861. Two calibers show up in most cases: the Seagull ST19, a hand-wind Chinese chronograph, and meca-quartz movements such as the Seiko VK64. The 1861 itself is real. Omega put it in the Speedmaster Professional Moonwatch from the mid-1990s until 2021.

What the real 1861 is

  • Hand wind. No rotor.
  • 18 jewels, 21,600 vph (3 Hz), 48-hour power reserve.
  • Cam-actuated chronograph. No column wheel.
  • Based on the Lemania 1873. Omega ran the 861 from 1968 and added the 1861 in the mid-1990s.
  • Subdials: 30-minute counter at 3 o'clock, 12-hour counter at 6, running seconds at 9.
  • Rhodium finish. The Omega name and the number 1861 sit on the bridges.
  • The 1863 uses the same base with Geneva stripes and a gold-plated finish for sapphire casebacks.
  • Omega replaced the 1861 with the 3861 in 2021. The 3861 adds a Co-Axial escapement, 26 jewels and a 50-hour reserve.

What sits inside a fake

Seagull ST19

The ST19 is a Venus 175 derivative from Tianjin Seagull. It is hand wind, runs at 21,600 vph, and uses the same 3-6-9 subdial layout. Bridge shape, engraving depth, screw heads and finish differ from the 1861. A timegrapher reads the same beat rate on both, so rate alone proves nothing.

Meca-quartz

Seiko VK64 and similar calibers run on a battery. The chronograph seconds hand moves in five steps per second. The running seconds hand ticks once per second. On many builds the 6 o'clock subdial is a 24-hour indicator, not a 12-hour counter. There is no winding feel at the crown.

Automatic clones

Some Speedmaster replicas use an ETA 7750 or an Asian copy. Those have a rotor. The 1861 does not. Subdial placement drifts too, because the 7750 puts its 30-minute counter near 12 o'clock.

Checks that work

  1. Caseback first. The 3570.50 Moonwatch has a steel caseback, so the movement is hidden. Photos of a closed back show nothing.
  2. Ask for photos with the back removed. Look for the 1861 stamp, bridge finish and jewel count.
  3. Look for a rotor. Any automatic winding block rules out an 1861.
  4. Wind to full and wait. A healthy 1861 runs about 48 hours.
  5. Start the chronograph. Count the steps of the center seconds hand. A sweep at 6 steps per second fits a mechanical caliber. Five steps per second fits meca-quartz.

Limits

Movement ID needs the watch in hand. Photos, listings and seller copy do not confirm a caliber. A watchmaker with a caseback tool and a timegrapher settles it in minutes. Until then, treat any 1861 claim on a replica as unverified.