There is no official synonym. Omega calls the movement calibre 1861, and that is the only name on the spec sheet. What people are really hunting for when they search a "synonym" is the workaround language sellers use, because most marketplaces block a listing that spells out the brand and the calibre together. You will see it relabeled as a hand-wound Lemania-style chronograph, an 1873 pattern movement, a Seagull ST19, or plain "1861-compatible." Those terms are not interchangeable, and knowing the gap between them is the whole point.
What the real 1861 is
The 1861 is the hand-wound chronograph Omega fits to the Moonwatch. Its family tree runs from the Lemania 1873 through the Omega 861, which arrived in 1968, to the 1861 in the mid 1990s, when the finish changed to rhodium plating. It beats at 18,000 vph, or 2.5 Hz, and uses cam and lever switching rather than a column wheel. Power reserve sits around 48 hours across 18 jewels. The 1863 is the same engine with decorative finishing for display backs.
The Ultimate Guide to Replica Omega Caliber 1861 Longtail Watches
That 18,000 vph figure matters more than any listing photo. It is the hardest spec to fake convincingly and the easiest one to check with a timing app and a quiet room.
Replica Omega Caliber 1861 En US
The names sellers substitute
- Seagull ST19 or ST1901. A Chinese column-wheel chronograph at 21,600 vph with roughly 40 hours of reserve. Common, serviceable, and not a copy of the 1861 in any real sense.
- Lemania 1873 pattern. Usually means the architecture was copied, not that Swiss parts are inside.
- Hand-wound 1861-style. Marketing filler. Ask for the beat rate and the jewel count instead.
- Venus 175 derivative. An older chronograph design reused by several Chinese factories.
How I check what is actually inside
I start with the subdial spacing, since a swapped movement rarely lines up perfectly with the case. Then the pushers: a cam-switched chrono has a soft, slightly vague start, while a column wheel clicks. Next comes the beat rate test, five beats per second for an 1861 versus six for an ST19. Finally the engraving. Real 1861 bridges carry crisp, shallow lettering; replica plates tend to look stamped and slightly off-center.
Before any money changes hands
Counterfeit watches are illegal to sell in the US and most of the EU, and customs does seize parcels. Nobody services these movements under warranty, and resale value is zero. If a listing leans on a vague synonym instead of naming the movement, treat that as the answer to your question.