Short answer

A Royal Oak listed as a 15311 is a numbering problem before it is a watch problem. Audemars Piguet's Royal Oaks in that size family are the 15300, the 15400, the 15500, and the Jumbo 15202. There is no catalog reference 15311 in the line. Any listing using that number is working from a typo, a seller's internal code, or a number invented to sound specific. A mismatch between the number in the listing and the reference on the caseback is the first tell, and it costs nothing to check.

Why the number matters more than the photos

Replica sellers use odd reference numbers because buyers search for models, not SKUs. If you type 15311 into a marketplace and get twenty hits at similar prices from shops you have never heard of, you are looking at a naming convention, not a watch. The real references have production windows you can verify. The 15300 ran from roughly 2005 to 2012, the 15400 replaced it, and the 15500 followed in 2019. Specs for each are published, so a listing should match one of them or explain itself.

Where the replicas come from

The Royal Oak is one of the most copied watches in the world, and the copies come in clear tiers. Cheap versions use plated cases, printed dials, and quartz movements. Mid-tier versions use a decorated automatic movement with a stamped rotor. The top tier, sold as 1:1 or super clone, copies case geometry closely and uses a clone movement. Even that tier gets small things wrong, and those small things are what you look for.

Dial tells

• The tapisserie grid should be raised, even, and sharp at the edges. On replicas the squares look flat, shallow, or uneven under raking light.
• Print should be crisp with no bleeding. Check the minute track and the small text under the logo.
• The applied AP logo sits above the date window on most references. On fakes it can sit low, sit high, or look stamped rather than polished.
• The date wheel should sit centered in the aperture with the font matching the rest of the dial. Off-center dates and mismatched numerals are common.
• There is no cyclops on a Royal Oak. If one is there, stop.

Case and bezel

Diameter and thickness are the hard numbers. A 15202 is a thin watch, and replica versions run thick because the clone movement sits taller than the original caliber. Measure with calipers if you can. The eight bezel screws are the other giveaway. On the original they are functional, with real slots cut into the heads. On many fakes the screws are decorative and the slots wander in different directions. Look at the bevels on the lugs too. Hand-finished chamfers catch light along a straight line, while machined edges look rounded and dull.

Bracelet and clasp

The bracelet tapers from the case to the clasp, and the links should have polished chamfers along both sides. Check the fit where the end links meet the case. Gaps, wobble, and sharp edges are signs of a copy. Genuine bracelets use screwed links, so look for flat-headed screws on the sides of the links. The clasp should close with a solid click and carry clean engraving.

Movement and caseback

Most Royal Oaks have a display back, so you get to look. Wave the watch near your ear: a Jumbo caliber beats slowly, at 19,800 vibrations per hour, while most clone movements run at 28,800. Rotor engraving, gear finishing, and jewel settings are where the money shows. Fakes tend to have shallow engraving, mirrored surfaces with no grain, and screws that sit proud. On the outside, caseback text should be cut deep and even, with a serial and reference number that follow AP's format.

Price and paperwork

A steel 15300 or 15400 trades in the five figures. Anything priced in the hundreds is a replica, and no amount of box and papers changes that. Papers themselves get faked, so match the serial on the caseback to the warranty card and the movement number where one exists.

Legal side, briefly

Buying a replica to wear is one thing. Selling one as genuine is trademark counterfeiting, which is a federal crime in the United States, and importing counterfeit watches can get a shipment seized by Customs. If you knowingly buy a replica, keep it as a replica and never pass it off.