Short answer
Most watches sold as a fake Audemars Piguet Royal Oak Perpetual 25659 do not copy the real movement. The original reference runs an Audemars Piguet calibre 2120/2802, a thin automatic base from the 1970s with a perpetual calendar module on top. Copies use a generic automatic or a quartz movement with printed dial details and apertures that do not work. The calendar on a copy needs a manual correction at the end of February. A real perpetual calendar does not.
Audemars Piguet has not published a full public spec sheet for every 25659 variant. Production years, metal codes and dial versions differ between auction records and dealer listings. Confirm anything number-specific with the manufacture archives before you rely on it.
What the reference is
The Royal Oak launched in 1972. Gerald Genta drew the case. The perpetual calendar version followed in the early 1980s and stayed in the catalogue for about a decade. Reference 25659 is one of the numbers in that family. Case metal codes sit in the reference suffix: BA for yellow gold, OR for rose gold, ST for steel, PT for platinum. A 25659 engraved with a code that does not match the case metal is a mismatch, not a rare variant.
Movement tells
- Running seconds. The 2120/2802 has no centre seconds hand. A watch with a sweeping seconds hand at the centre is not built on that base.
- Aperture count and position. The calendar reads month and leap year, day, date and moonphase. Count them. Print that sits off centre under an aperture is a dial print problem.
- February behaviour. Set the watch to 28 February and let it run. A perpetual calendar rolls to 1 March in a non-leap year.
- Moonphase accuracy. A gold moon disc with a printed star field is normal. Photo-printed or plastic discs are not.
- Winding feel. Calibre 2120 winds through a full rotor. A loud, loose rotor points to a cheap base movement. That is not proof, but it is a prompt to open the back.
Case, dial and finish
Real 25659 cases are solid gold or steel, not plated. Weigh the watch. A plated brass case with a gold tone has a different heft and a different feel at the crown. Check the hallmarks inside the caseback and on the caseback edge. Swiss gold hallmarks changed over the period, so the mark must match the stated production year.
The dial is the second check. Print edges on a fake are soft under magnification. The applied indexes on the original sit flush with even gaps to the chapter ring. The signature and the line under it use specific letter widths.
Caseback and numbers
The reference, case number and movement number are engraved. On a fake, engraving depth is uneven and fonts drift between watches from the same seller. Compare two watches from one source. Matching fonts across unrelated references is a warning sign.
Limits of a photograph
No photo check proves authenticity. A watchmaker with the movement in hand can verify the base calibre, the module, the jewelling and the engraving. Auction houses publish condition reports for real examples. Use those reports to learn what an untouched example looks like.
Price context
Vintage Royal Oak perpetual calendars sell in the five-figure USD range at auction, with premiums for platinum, box and papers, and original finishing. Listings far below that range are a claim, not a bargain.