Short answer
A replica Omega Caliber 8605 is not a copy of the real movement. The genuine Caliber 8605 is an automatic Co-Axial chronograph with twin barrels, a 60-hour power reserve, a silicon balance spring and a 4 Hz beat rate. Replica examples sold as super clone 8605 movements are built from an Asian 7750, a Chinese chronograph module, or a quartz unit dressed with fake bridges. The decoration, not the caseback engraving, is where most of them fail inspection.
What the genuine Caliber 8605 does
Omega built the 8605 on the 8500 family architecture. Two mainspring barrels sit in series and feed a Co-Axial escapement, which cuts sliding friction at the pallet stones. A silicon balance spring resists magnetism and temperature drift. The chronograph runs off a module stacked on the base movement, with central seconds and two counters. Power reserve is 60 hours, the beat rate is 28,800 vibrations per hour, and the jewel count sits in the high 30s.
How replica versions are built
Most replica 8605 movements start as an Asian 7750 or a Seagull chronograph. Builders add an engraved rotor, printed plates and a decorative bridge to imitate the arabesque Geneva waves on the genuine. Some use a quartz module and hide it behind a solid caseback. A small number attempt a true clone with a modified gear train, but the escapement stays a standard Swiss lever. That single fact makes verification simple.
How to verify one
- Wind the crown 40 full turns with the watch stopped.
- Set the hands to 12:00 and write down the exact time.
- Leave the watch dial up in a drawer for 60 hours.
- Compare the reading against your written time.
- Install a timegrapher app and measure the beat rate at full wind.
- Remove the caseback with a rubber ball or a two-prong wrench.
- Read the rotor engraving under a 10x loupe.
- Trace the balance spring from the stud to the collet.
- Count the teeth on the escape wheel.
- Press the chronograph start, stop and reset pushers in sequence.
- Compare the plate finish against photos of the genuine caliber.
What each check reveals
- 60-hour reserve: a real twin-barrel 8605 holds 58 to 62 hours. An Asian 7750 base stops between 38 and 44 hours.
- Beat rate: 28,800 vph shows as a clean 4 Hz trace. Slower clones read 21,600 vph with heavy amplitude scatter.
- Rotor text: genuine engraving is crisp, deep and correctly kerned. Replicas show shallow laser etching and wrong letter spacing on Co-Axial.
- Balance spring: silicon reads matte dark gray with a flat, uniform hue. Steel reads bright and reflective.
- Escape wheel: Co-Axial teeth are three-pronged and rounded. A standard lever escapement shows a flat, pointed tooth profile.
- Chronograph reset: genuine hands snap back in one motion. Module-based replicas lag or overshoot by a fraction of a second.
- Plate finish: genuine arabesque waves are cut, not printed. Replicas show a repeating stamped pattern that flattens under raking light.
Service and lifespan
Replica 8605 movements are not supported by Omega or any authorized service center. Parts come from the same aftermarket channels that built the watch, and a 7750-based replica can be serviced by an independent watchmaker who works on Chinese chronographs. Expect a 3 to 5 year interval, a cleaning, and a fresh gasket set. A quartz stand-in needs only a battery and a seal check. If a seller claims a Swiss made 8605 inside a replica case, treat that as a red flag, because Omega does not release this caliber to third parties.