The short answer: a good fake Audemars Piguet Royal Oak Offshore 26420 can get the silhouette and the dial texture close, but none of them replicate what sits inside. The real 26420 uses AP's in-house caliber 4404, a flyback chronograph with a 70 hour power reserve. Replicas run on modified Asian chronograph movements, so the pushers feel different, the counters behave differently, and the case almost always runs thicker than 14.4mm. Judge the good ones on those terms and you will not be disappointed or overcharged.
What the genuine 26420 actually is
- 42mm stainless steel case, listed at 14.4mm thick, 100m water resistance
- Caliber 4404: automatic, flyback chronograph, 30 minute and 12 hour counters, date, 70 hour reserve
- Mega Tapisserie dial, ceramic bezel on several references, sapphire front and back
- Quick release strap system, so bands swap without tools
Those numbers matter because they are the yardstick every replica gets measured against. A copy that lands at 16mm thick is not a near miss, it is a different watch on the wrist.
How close the replicas get
There are roughly three tiers. Cheap builds use quartz or basic automatic movements with dead subdials, and the case is usually too thick and too shiny. Mid tier watches use a 7750 derived automatic with working counters, decent dial printing, and a body around 15.5mm to 16mm. The top tier uses a decorated clone or heavily modified movement, a slimmer mid case, better Tapisserie squares, and a bracelet or rubber strap that feels closer to the original.
What I would inspect first
- Thickness. Measure it with calipers if you can. Anything over 15.5mm is obvious next to a real one.
- Subdials. All three should move and reset. On many fakes the running seconds is the only thing that works.
- Dial texture. Mega Tapisserie squares should be crisp with sharp edges and even spacing, not soft bumps.
- Date window. Font, position, and the magnifier if the reference has one. This is where budget copies give themselves away.
- Bezel screws. They should sit flat, line up evenly, and slot into the bezel without chewing the edges.
- Crown and pushers. Screw down smoothly, no wobble, chronograph pushers with a firm click.
- Caseback and clasp. Engraving depth and font weight are usually the last thing a factory perfects.
Where every replica falls short
The movement is the honest dividing line. No copy uses a real 4404, and the finishing on bridges and rotors is cosmetic rather than functional. Water resistance is claimed, rarely tested, so keep any fake away from swimming pools and showers. Weight is another tell: the real steel case and bracelet have a density that cloned hardware tends to miss, and a light watch on a heavy looking bracelet is a common giveaway.
Quick checklist before you pay
Ask for the measured thickness, a photo of the movement through the caseback, a video of the chronograph starting, stopping and resetting, and a shot of the date at a single digit and a double digit. If a seller will not supply those four things, the watch is not worth the money, whatever the listing claims.
One more thing worth saying plainly: buying a replica is legal in most places, but selling counterfeit branded goods is not, and wearing one as the real thing will not survive a close look. Treat it as a fun homage and you will enjoy it more.