The replica Omega caliber 8605 is a cloned automatic chronograph movement with a GMT function, built to match the appearance of the genuine Omega 8605 caliber from the brand's Co-Axial generation. Most replicas get there with a decorated Asian 7750 base, a GMT module, an engraved rotor, and bridge plates finished to resemble the Swiss original. Performance varies a lot between sellers, so the movement is the single most important thing to inspect before you buy.
One caveat up front: replica watches are not Omega products. Omega, Co-Axial, and the caliber numbers are trademarks of Omega SA, and the clone exists only as an imitation of the real design.
What the Genuine 8605 Represents
The 8605 belongs to the 8500-family generation Omega introduced in the late 2000s. That family is known for a Co-Axial escapement, twin series-coupled barrels, a silicon balance spring, and a long power reserve for an automatic chronograph. Adding a GMT function to a chronograph base makes the movement harder to copy well, because the extra hand and gearing sit on top of an already crowded chronograph stack.
Specifications shift by reference and by year, so confirm which base watch a dealer is copying. A build made for one reference will not simply drop into another.
How the Clone Is Usually Built
Almost every replica 8605 relies on a Valjoux 7750 style architecture, the standard foundation for affordable automatic chronographs. Makers then add:
- A GMT module or adapted 24-hour gearing driving the fourth hand
- A rotor engraved with Omega style markings and a caliber number
- Striped bridges, blued or polished screws, and plated wheels
- A display case back engineered to show off the decorated platework
Because the base is a proven workhorse design, the replica can keep decent time and run a real 12-hour chronograph. What it does not reproduce is the Co-Axial escapement or the silicon balance spring. Those are Swiss parts, and clones in this class rarely attempt to copy them functionally.
What to Check Before You Buy
- Pusher feel: start, stop, and reset should be crisp with no grinding.
- GMT hand: find out whether it sets independently or is linked to the hour hand, then check alignment to the markers.
- Date change: it should flip around midnight, not drift through it.
- Rotor: listen for scraping, and confirm it spins when the watch is tilted.
- Engraving: caliber text, font, and spacing are the fastest giveaway on a display back.
- Power reserve: wind it fully, set it down, and time how long it runs.
Common Tells on a Weak Example
A cheap replica 8605 usually fails in the same places. The rotor text looks laser-etched rather than engraved, the striped finish runs the wrong direction, screws are painted instead of heat-blued, and the balance assembly looks nothing like a genuine Omega unit. Mushy pushers or a chronograph hand that snaps back past zero are mechanical faults, not cosmetic ones.
Markings matter too. Swiss labeling rules restrict when "Swiss Made" can legally appear, so a movement stamped that way with obvious budget finishing is a labeling problem as much as a quality one.
Service, Care, and Lifespan
The upside of a 7750-derived clone is parts availability. Independent watchmakers can service the base movement, replace a worn chronograph wheel, or regulate it. Plan on a service interval of a few years, avoid pressing the pushers while the watch is wet, and keep it away from steam and hot showers unless the case has been pressure tested. A maintained replica caliber 8605 can run for years. A neglected one will start losing time or stalling the chronograph.
Matching the Movement to the Case
Not every clone fits every case. Movement diameter, stem height, date wheel position, and the height of the GMT hand stack all have to line up with the case and dial. That is why the better replica Omega caliber 8605 builds come from sellers who publish movement photos and case measurements instead of a stock image. Ask for a photo of the actual movement inside the actual watch.
Bottom Line
Judge the replica 8605 as a movement, not as a marketing line. If the pushers are sharp, the GMT hand aligns, the rotor engraving matches the reference, and the power reserve holds overnight, you have one of the better chronograph clones. If any of those fall short, the rest of the watch rarely makes up for it.