Quick answer
If you are shopping for a replica Speedmaster automatic, you are looking at a copy of one of Omega's self-winding chronographs, not the Moonwatch. The Speedmaster Professional that went to the Moon runs on a hand-wound movement, so a genuine automatic Speedmaster belongs to a different family of watches: the Reduced, the Date and Day-Date, the Racing, and the '57. Replica makers follow those references because the real ones already used a self-winding base caliber, which makes the copy easier to build and easier to wear convincingly.
The short version: expect an Asian 7750 or a Seagull chronograph inside, a 39mm to 41.5mm case depending on the reference being copied, and quality that swings hard between sellers. Subdial spacing and case thickness give most fakes away.
Which Speedmaster references are automatic
Getting the reference right matters, because it decides case size, dial layout, and which movement the replica should have.
- Speedmaster Reduced (3510.50, 3539.50 and relatives): 39mm case, 18mm lugs, ETA 2892 base with a Dubois-Depraz chronograph module stacked on top. That module is why the subdials sit far apart and why the case is thicker than the number suggests.
- Speedmaster Date and Day-Date: 39mm, Valjoux 7750 family inside, subdials at 12, 6 and 9 with the date or day window at 3.
- Speedmaster Racing: 40mm, Co-Axial automatic, busier dial with a racing scale.
- Speedmaster '57: 41.5mm, Co-Axial automatic, no crown guards, straight lugs.
None of these are the Moonwatch. If a seller calls a self-winding watch a Moonwatch automatic, they either do not know the product or they are counting on you not knowing it.
Movements you will actually find
The Asia 7750 is the default. It clones the Valjoux 7750, it winds with a rotor, and it runs a 12 hour chronograph counter. In a Speedmaster Date replica that layout is close to correct. In a Reduced replica it is not, because the genuine watch is a modular design and the 7750 pushes the subdials to different positions on the dial.
Some builders use a Seagull ST19 or ST1901, which is hand-wound. That can look right on a Moonwatch copy but it is wrong on anything sold as automatic.
A few sellers advertise super clone Speedmaster automatics. Treat that phrase as marketing for a well-finished 7750 build, not a cloned Omega 9900. Nobody is machining a true copy of Omega's Co-Axial chronograph movement at replica prices, and anyone who says otherwise is selling you a story.
What separates a solid build from a bad one
- Subdial spacing. On a Reduced copy the chronograph subdials should sit close to the center of the dial. If they spread out toward the edge, the case is hiding a 7750 and the proportions will look off in person.
- Case thickness. Modular and 7750-based chronographs are chunky. Compare the listed thickness against the genuine spec before you buy.
- Pusher feel. A good 7750 build has a firm start and stop with a crisp reset. Mushy pushers usually mean a cheap movement or sloppy assembly.
- Bezel print. Tachymeter numbers should be sharp and evenly spaced, with the dot over 90 detail correct for the reference being copied.
- Crystal. Genuine Speedmasters vary between hesalite and sapphire. A cloudy or heavily blue crystal is an easy tell across a table.
- Lume. Applied indices with a flat, even fill. Bubbled or patchy lume shows up constantly at the low end.
Fit and wrist presence
The Reduced is the one most people want, and it wears smaller than 39mm suggests because the lugs are short and the bracelet tapers to 18mm. On a 7 inch wrist it sits flat and neat. The Racing and the '57 wear bigger and thicker, so on a smaller wrist a 41.5mm automatic chronograph copy feels like a slab.
Before you pay
Ask for photos of the actual watch, a timing machine reading, and a look at the caseback if the seller will open it. Ask which movement is inside, what the case measures front to back, and what the return window covers. Sellers who answer those questions in detail tend to be the ones whose watches match the listing. Sellers who send stock photos and a price are a coin flip.