Quick answer

A fake Speedmaster 42mm shows wrong case size, wrong movement, and wrong dial text. Real Omega Speedmaster Professional cases measure 42mm across. Many fakes measure 40mm or 44mm. The real watch has a hand-wound movement. Fakes use quartz or cheap automatic movements. Check the caseback reference, the subdial spacing, and the crystal material.

Case and dimensions

Omega lists the Speedmaster Professional Moonwatch at 42mm diameter, 13.2mm thick, and 47.5mm lug to lug. A caliper check takes 10 seconds. Fakes often miss the lug-to-lug number by 2mm or more. The real case has twisted lugs. Fakes use straight lugs or a one-piece case.

Movement

The current Moonwatch uses calibre 3861. Older models use 1861 or 861. All are hand-wound. A fake with a quartz movement has a seconds hand that ticks once per second. A real Speedmaster has a sweeping seconds hand at 21,600 vibrations per hour. Some fakes use an automatic movement with a rotor. The real Moonwatch has no rotor.

Dial and hands

Real subdials sit close to the center. Fakes push subdials outward. The word Speedmaster on the real dial uses a specific font. The letter a has a flat top. Fakes use a round top. The tachymeter bezel on the real watch has a dot over 90. Fakes often print the dot next to 90.

Caseback and serial

Real casebacks have a seahorse medallion and a serial number. The serial is 8 digits. Fakes use wrong fonts, missing numbers, or a sticker. A real Speedmaster has a reference number on the inside of the caseback. You need a caseback tool to see it.

Crystal and bracelet

Real Moonwatch crystals are hesalite or sapphire. Hesalite feels warm and shows scratches. Sapphire feels cool and resists scratches. Fakes use mineral glass or acrylic with a wrong stamp. Real bracelets have 20mm lugs and a signed clasp. Fakes use 18mm or 22mm lugs and a blank clasp.

Price and seller

A real Speedmaster Professional costs $6,000 to $8,000 new. A used model costs $4,000 to $6,000. A fake sells for $50 to $300. A price below $3,000 for a new watch points to a fake. Buy from an authorized dealer or a trusted seller with papers.