Audemars Piguet has never catalogued a Royal Oak with the reference number 15311. The number does not appear in AP's reference system, in auction archives, or in service records. A watch advertised as a "Royal Oak 15311" is therefore one of three things: a mistyped 15300, a relabeled counterfeit, or a fabricated number used to make a replica listing look specific and credible. This guide covers the reference system and the checks that separate a genuine Royal Oak from a fake.

Why 15311 Is Not a Real Reference

Audemars Piguet reference strings combine a core case number with metal and bracelet codes, for example 15300ST.OO.1220ST.01. The five-digit core identifies the model family. The letter blocks identify steel (ST), yellow or rose gold (BA, OR), titanium (TI), and the bracelet or strap that shipped with the watch. "15311" matches no core number in AP's published catalog, and the 153xx range holds no Royal Oak model beyond the 15300 and its variants.

Genuine References That Get Confused With 15311

  • 15300ST: 39 mm Royal Oak, caliber 3120, date at 3 o'clock.
  • 15202ST: 39 mm Extra-Thin Jumbo, caliber 2121, no seconds hand.
  • 15400ST and 15500ST: 41 mm Royal Oak with date at 3 o'clock.
  • 16202ST: current 39 mm Jumbo with caliber 7121.
  • 26331ST: 41 mm Royal Oak Chronograph with two counters.

How to Check a Watch Sold as a 15311

  1. Ask for the full engraved reference string from the caseback and compare it against AP's catalog. A seller who cannot produce that string is describing a watch they cannot verify.
  2. Measure the case across the bezel at its widest point, with the crown excluded. A 39 mm Royal Oak measures about 39 mm. A 41 mm measures about 41 mm. Replica cases often run half a millimeter to a millimeter off.
  3. Study the dial. Royal Oak dials use a tapisserie pattern with a fine raised grid, an applied AP logo, and a date window aligned with the 3 o'clock marker. Printed logos and date apertures that sit low or high point to a fake.
  4. Inspect the caseback engraving. Genuine engraving is crisp, shallow, and machine cut. It carries the reference number, the serial, and Swiss made text inside the octagonal bezel screws.
  5. Examine the bracelet. Genuine Royal Oak links taper from the lug to the clasp and the polished bevel edges stay straight. Fakes show rounded bevels, soft edges, and uneven gaps between links.
  6. Request movement photos. Genuine Royal Oak automatics run calibers 2121, 3120, 4302, or 7121 with Geneva stripes, chamfered bridges, and a signed rotor. Replica movements show stamped plates and unbranded rotors.
  7. Verify the serial with an authorized AP service center or an independent watchmaker who works on Audemars Piguet. Photo authentication alone is not reliable.

Common Red Flags

  • Reference numbers that do not exist, including 15311.
  • Prices far below the current market for the stated model.
  • Listing photos lifted from auction houses or review sites.
  • No caseback photo, or a caseback photo that is blurred at the engraving.
  • A seller who cannot name the caliber.
  • Pressure to pay through a channel with no buyer protection.

Legal and Practical Notes for US Buyers

Trafficking in counterfeit goods is a federal crime in the United States under 18 U.S.C. 2320, and US Customs and Border Protection can seize counterfeit watches at the border. Audemars Piguet will not service or authenticate a counterfeit, no factory warranty transfers, and the watch carries no resale value in the legitimate market. Counterfeit Royal Oaks also skip the finishing steps that define the model: hand-applied bevels, black-polished screws, and a movement regulated to tight tolerances. If the goal is ownership of a Royal Oak, confirm the reference number first. 15311 fails that test, and any watch sold under it should be treated as unverified.