Quick answer
Omega caliber 8605 is an automatic Swiss movement. It has a co-axial escapement, two mainspring barrels, a 60-hour power reserve, a date window and a 24-hour GMT hand. Omega fitted it to Seamaster Aqua Terra GMT and Planet Ocean GMT models. A "replica Omega caliber 8605" is the movement inside a counterfeit copy of those watches. No replica 8605 carries a real co-axial escapement. Most replicas use a Chinese automatic movement with a decorated plate and a rotor stamped to look like the Omega part.
Caliber 8605 specs
- Type: automatic, bi-directional winding
- Escapement: three-level co-axial
- Beat rate: 25,200 vibrations per hour (3.5 Hz)
- Jewels: 39
- Power reserve: 60 hours, two barrels in series
- Balance spring: silicon (Si14)
- Functions: hours, minutes, seconds, date, GMT 24-hour hand
- Magnetic resistance: 15,000 gauss on the Master Chronometer version
What replica listings call an 8605
Sellers use the name for the movement in fake Aqua Terra GMT and Planet Ocean GMT watches. The movement inside is a Chinese automatic, in most cases a 2824-type or 2892-type clone with a GMT module added. Beat rate is a fast check. Clones run at 28,800 vibrations per hour. Cheaper GMT movements run at 21,600. Caliber 8605 runs at 25,200, a number no common clone matches.
Jewel count and escapement are the other gaps. A clone has a Swiss lever escapement, not a co-axial. Stamped text on the rotor may read 39 jewels while the movement holds fewer. The silicon balance spring and the twin barrels have no equivalent in the copies.
Checks that work from photos
- Ask for the beat rate in numbers, not a description.
- Ask for a clear photo of the balance wheel and the escapement below it.
- For a Master Chronometer version, ask for the card and its number. METAS certifies each watch and the number can be checked.
- Compare rotor engraving depth, font and jewel count with Omega catalog photos.
Legal status in the US
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. 2320. Penalties for an individual on a first offense reach 10 years in prison and a $2,000,000 fine. US Customs and Border Protection can seize and destroy counterfeit watches at import. Resale carries separate civil liability to the trademark owner.
What is not known
Factories change movement suppliers without notice, so a listing photo from last year may not match the watch shipped this year. No public test data exists for replica 8605 movements. Claims about 1:1 construction come from sellers, not from measurement.