Short answer
No replica uses the Omega caliber 3861. Omega builds the 3861 in Switzerland. Copy sellers print 3861 on a listing because the number draws searches. The movement inside a copy is a Seagull ST19, a clone of the Lemania 1873 pattern, or a low-grade quartz module.
The real caliber 3861
Omega launched the 3861 in 2021 inside the Speedmaster Professional Moonwatch. It replaced the 1861. Specs: manual wind, co-axial escapement, 26 jewels, 21,600 vibrations per hour, 50-hour power reserve, silicon balance spring. Omega submits each movement to METAS for Master Chronometer certification. That test set covers eight criteria, including magnetic fields to 15,000 gauss and rate in several positions and temperatures. The older 1861 had 18 jewels, 48 hours of reserve, and no METAS card.
What the copies use
Most 3861-labeled copies carry the Seagull ST19. Tianjin Seagull builds the ST19 as a column-wheel chronograph. Ratings: 21,600 vph, roughly 40 hours of reserve, lever escapement, alloy hairspring. Jewel count varies by version. Sellers add a decorative bridge plate and engraved text to mimic the 3861 finish. The plate covers the balance and adds no function. A second group uses a Lemania 1873 pattern clone. Both movements lack the co-axial escapement, the silicon spring, and the METAS test.
Differences a buyer can check
- Movement number: the real 3861 has a serial and a METAS card with a matching number. Copies ship with a blank card or no card.
- Escapement: the real 3861 has two escape wheels in a co-axial stack. A copy has one escape wheel.
- Hairspring: silicon appears dark gray. Alloy hairsprings are blue or silver.
- Price: real 3861 Moonwatches sell for about $7,000 and up in the US. Copies sell for $80 to $500.
- Caseback text: real engraving is deep and crisp. Copy text is stamped with shallow relief.
Legal status in the US
A watch with an Omega logo and no Omega authorization is a counterfeit good. Import into the US violates 19 U.S.C. 1526 and 15 U.S.C. 1124. CBP officers seize such shipments. Penalties can include forfeiture of the goods and civil fines. Selling them in the US is trademark infringement.
What is unknown
Movement numbers on a sales page do not confirm the caliber inside. Copy factories change suppliers with no notice. No public lab data covers how a copy 3861 holds rate over months. Claims of a "Swiss 3861 clone" have no verifiable source.