The Audemars Piguet Royal Oak Offshore 25940 is the Rubberclad, a 42mm chronograph AP built from about 2002 into the early 2010s. If you are sizing up a fake, the tells land in the same three places every time: the case profile, the rubber on the bezel and pushers, and the movement. Everything else can be copied well enough to survive a listing photo.
What the 25940 actually is
The 25940 belongs to the first generation of Royal Oak Offshore chronographs, the line that took the 1972 Royal Oak and made it wider, taller, and louder. AP used the reference across several dial and metal combinations, but the one most people mean is the Rubberclad: steel case, rubber-clad bezel, rubber-coated crown and pushers, rubber strap. Diameter is 42mm and the case sits close to 14mm tall on the wrist.
Under the dial, AP lists the 25940 with Calibre 2326/2840, a modular chronograph built on a Frederic Piguet base. It runs at 21,600 vibrations per hour. The finishing on that movement, and the way the chronograph feels when you start and stop it, are the parts of this watch that no replica factory has managed to reproduce at a price anyone wants to pay.
Why this reference gets copied so much
Two reasons. The rubber bezel and rubber pushers look simple, so the copy houses assumed they would be easy. They are not, because vulcanized rubber has a specific matte grain and a specific edge where it meets the steel. The second reason is demand. The Rubberclad was the Offshore that made the Offshore famous in the 2000s, so it carries recognition without the price of a modern 26470.
That combination puts a lot of 25940 fakes into circulation, and plenty of them get sold as genuine by people who know exactly what they are doing.
Case and crystal: where fakes lose first
Measure the thickness before you look at anything else. A 25940 that comes in at 11mm or 17mm is not a 25940. Fakes built on a 44mm Offshore case are the other common shortcut, and the giveaway is the bezel to case ratio, which looks stretched on the larger shell.
Run a fingernail along the case flank. Genuine Royal Oak finishing has a crisp break between the brushed top surface and the polished bevel, and that break should be even from lug to lug. On a fake it wanders, or the brushing is coarse enough to catch light in a straight line.
Check the crystal from the side. It should sit slightly proud of the bezel with a clean edge and no rainbow tint at the rim. Cheap sapphire or mineral substitutes show a blue or purple cast at an angle, and they distort the dial print near the edge.
Rubber, bezel, and pushers
Look at the bezel under a lamp, not under a phone flash. Genuine rubber has a flat, dry finish. Replicas usually come out slick or greasy, and the edges where the rubber meets the octagonal steel ring are rounded instead of sharp.
The pushers deserve their own check. They are rubber-coated and screw down, and they should still feel firm with a short, clean travel when you work the chronograph. If the rubber is missing, or if the pushers are plain brushed steel, stop there.
Dial and date
The three subdials sit at 12, 9, and 6, and the print on them should be sharp enough to read at arm's length without squinting. Fakes usually go wrong with the subdial rings, which come out too thick, and with hand length, which stops short of the markers.
AP's date aperture on this reference is crisp and square cut. Look for a printed date that sits low in the window, or a window with a bevel that was machined after the dial was painted. Both are common on replicas.
Lume is another quick test. Genuine markers glow soft green or blue, fade over a few hours, and never look chalky in daylight.
The movement is the hard part
Most 25940 replicas run a Valjoux 7750 derivative or a quartz module. The 7750 is a real chronograph movement and it will fool someone who only looks at the dial, but the subdial functions and the position of the running seconds do not match the AP caliber, and the rotor and bridges look nothing like AP finishing.
If the caseback is a display back, use a loupe. Anglage on the bridges, perlage on the plates, and an engraved rotor are all things the genuine watch has and the replica does not. If you cannot see the movement, ask why, and ask for a photo with the back off.
Caseback engravings and paperwork
Engraving depth is a good filter. Genuine AP stamps the reference, the case serial, and the movement number deep enough that you can feel them with a fingertip. Lasered copies sit shallow and look grey instead of bright.
Papers and boxes are the easiest thing in this hobby to fake, so treat them as a nice extra rather than proof. The watch is the evidence.
What to ask before you pay
- Case thickness and diameter, measured with calipers, in writing.
- A photo of the movement, not a stock image.
- The reference and serial numbers from the caseback, checked against AP records or a watchmaker database.
- Service history, because a 2326/2840 that has never been serviced will need one.
- Whether the rubber bezel has been replaced, and with what.
One honest note on the legal side
Counterfeit watches are illegal to import and sell in the United States, and Customs seizes them. Plenty of buyers treat replicas as a cheap way to wear a shape they like, and that is a personal call, but the risk is real and it does not disappear because a seller calls it a homage or AAA grade. If you want the 25940 look with no legal exposure, the honest options are a genuine pre-owned example or a microbrand that borrows nothing but the octagon.