Short answer

A fake Audemars Piguet Royal Oak Offshore 26403 is a watch built to copy the Offshore Chronograph look. It was not made by Audemars Piguet. Two things share this name. One is a counterfeit sold as a genuine AP. The other is a replica sold as a replica. The checks below apply to both.

Note: reference 26403 is not one of the Offshore references with thick public documentation. Collector sources list many Offshore Chronograph numbers, from 25721 in 1993 to 26420 in 2021. For a 26403 offer, ask the seller for a caseback photo, the reference number and a movement photo. If the seller cannot supply them, stop.

What the reference line is

The Royal Oak Offshore arrived in 1993. Designer Emmanuel Gueit worked from the 1972 Royal Oak drawn by Gerald Genta. The main parts have not changed since: octagonal bezel, eight hexagonal screws, thick case, rubber strap options, tapisserie dial grid.

Offshore Chronograph references in the 26400 and 26470 range use the octagonal screw bezel, a screw-down crown and two pushers at 4 and 2 o'clock. Case size sits at 42mm or 44mm. The 42mm chronograph runs calibre 3126/3840, a Frederic Piguet 1185 base with a chronograph module. That number matters when you check a watch.

Checks that catch most counterfeits

  • Caseback text. Look at stroke width, letter spacing and depth. Genuine engraving cuts the metal. Many fakes print on top.
  • Serial and reference numbers. Ask Audemars Piguet to confirm the number. One number listed by two sellers is a red flag.
  • Movement. Pull the caseback photo. The 3126/3840 has a signed rotor, Geneva stripes and blued screws. Common counterfeit bases are an ETA 7750 or a Seagull clone. Rotor text sits low and the finish looks flat.
  • Date wheel. Check the font. Thin, small or wrong-shaped numbers show up often.
  • Tapisserie grid. Count the squares across the dial against a photo of the same reference. Squares that run into the date window or the subdials show a copy.
  • Pushers. Genuine pushers turn with two fingers and feel dry and firm. Loose or grinding pushers point to a copy.
  • Weight. Steel Offshore chronographs are heavy. A light case points to plated brass or alloy.
  • Box, papers and price. A full set at a price far under market means the set is fake, the watch is fake, or both.

What replica buyers check

Replicas of this model come in tiers. The cheap tier uses quartz or a low-grade automatic movement and a printed dial. The mid tier adds a 7750 clone and better dial texture. The top tier copies the case profile, the crystal shape and the strap fit.

Flaws reported by owners: case thickness runs 1mm to 2mm over spec, date font is wrong, lume fades fast, bezel screws sit proud, and the movement does not behave like a module movement. Ask for a timegrapher photo and a video of the chronograph start, stop and reset. Reset to zero on every run is a basic test.

Limits of any check

Photos hide polishing and repair. A counterfeit can pass a photo review and fail in the hand. If you cannot inspect the watch, use a payment method with a refund path. Meet at a watchmaker who can open the caseback.

Legal note

U.S. law bars the import and sale of counterfeit goods. Counterfeit watches face seizure by Customs and Border Protection. Selling a replica as a genuine Audemars Piguet is fraud. A genuine watch can go to Audemars Piguet for service. A replica cannot.

Specs to compare

  • Bezel: octagonal, eight hexagonal screws.
  • Case: steel or gold, 42mm or 44mm by reference.
  • Movement: calibre 3126/3840 on the 42mm chronograph group.
  • Dial: tapisserie grid, three subdials plus date on chronograph models.
  • Thickness and water resistance: confirm against the AP spec sheet for the exact reference.