The short answer: for a Caliber 8605 replica, buy the version built on an Asian 2836-2 with a GMT module and a decorated 8605-style bridge, rotor and balance cock. It keeps a 4 Hz sweep, the GMT hand sets independently, and most watchmakers will touch it. I judge every 8605 rep on five points: how the GMT hand sets, beat rate and power reserve, decoration fidelity against the real Co-Axial layout, case thickness and date window position, and whether spare parts exist outside the factory. The sections below compare the replica movement with the genuine 8605 and with the other clone routes you will see in listings.
What Caliber 8605 Actually Is
Caliber 8605 is Omega's Co-Axial GMT movement from the 8500 family: twin barrels, a 60-hour power reserve, a silicon Si14 balance spring on later examples, and a 25,200 vph (3.5 Hz) free-sprung balance. It powered Aqua Terra GMT and Planet Ocean GMT references, and later versions carry the Master Co-Axial name on the dial. None of that architecture exists in a replica at this price. What factories copy is the view through the caseback: rotor engraving, arabesque bridge shapes, blackened screws, Co-Axial lettering, and the correct caliber stamp.
Replica 8605 vs Genuine 8605
This is the comparison that matters if you already know the watch. The genuine movement is an integrated GMT with a jumping local hour hand, twin series-coupled barrels, and a silicon hairspring that shrugs off magnetism. The replica is a three-hand base caliber with a GMT wheel stacked on top, dressed to look like the real thing. From across a table the difference is invisible. Under a loupe, or after a week on the wrist, it is not.
Pros
- Correct dial-side behavior: the GMT hand tracks a second time zone and the date still flips at midnight.
- Decoration gets the major cues right, including rotor text, bridge color and screw heads.
- Caseback thickness on the better 1:1 cases stays close to the genuine profile.
- Replacement cost is low enough that a service is optional rather than mandatory.
Cons
- No twin barrels, so power reserve lands near 38 to 42 hours instead of 60.
- No silicon hairspring and no free-sprung balance; you get a regulator index instead.
- Engraving is stamped or laser-cut, not applied with the depth of a genuine bridge.
- Genuine parts do not interchange, so any failure means a full movement swap.
Replica 8605 vs Asian 2836-2 GMT Build
Most honest listings describe the same thing in different words. The "clone 8605" and the "2836 GMT" are usually the same Asian base caliber with different decoration and different marketing. The 2836-2 route wins because the base is common, proven, and repairable, and because it beats at 28,800 vph, which is closer to the visual smoothness people expect from a modern Omega than a 21,600 vph substitute.
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Pros
- Base caliber is widely stocked, so a movement swap costs less than a repair.
- 4 Hz beat rate gives a clean sweep, and the seconds hand starts without stutter.
- Independent GMT setting is quick to use and easy to explain to a watchmaker.
- Thinner stack than a dressed-up fake Co-Axial, which helps the case sit correctly.
Cons
- GMT module is the weak link; hand-setting force should stay gentle.
- Rotor noise and winding feel are coarser than the decorated bridge suggests.
- Date font and window position vary by batch, so check photos against the reference you want.
- Magnetism resistance is ordinary steel-level, not silicon-level.
How to Judge an 8605 Replica Before You Pay
- Ask for a caseback photo in daylight. Look for engraved, not painted, caliber text.
- Confirm the GMT hand sets independently in the middle crown position, not by turning the bezel.
- Check the balance through the back: a regulator index means base caliber, which is expected.
- Compare crown height and caseback depth to reference photos; a domed back is a giveaway.
- Ask what movement is inside in plain words. A seller who says "clone 8605" without naming the base is guessing.
Use Case Recommendations
If you travel and actually use a second time zone, take the 2836-2 GMT build and treat it as a wearable tool with a service life of a few years. If the watch is a display piece and the caseback matters more than the beat rate, the decorated 8605-style version photographs better. If you want a movement you can hand to any watchmaker without explanation, skip the GMT complication and buy a plain three-hand Aqua Terra replica instead. If you expect genuine-level finishing, magnetic resistance or a 60-hour reserve, no replica at this tier delivers it, and a mid-range Swiss or Japanese GMT is the honest path.