Short answer
A fake Audemars Piguet Royal Oak Offshore ref. 26420 copies a 43mm chronograph that AP released in 2021. Genuine 26420 watches run the in-house calibre 4401, a column-wheel flyback chronograph with a 70-hour power reserve and a sapphire caseback. Copies fall into two groups: mid-tier builds with a decorated ETA 7750 base, and top-tier builds with a clone 4401 and a case close to the real 43mm. The gap shows in the movement, the dial print, the caseback engraving and the weight.
What the 26420 is
Audemars Piguet launched the Royal Oak Offshore in 1993. The 26420 line arrived in 2021 with a 43mm case, replacing the earlier 44mm Offshore chronographs. Water resistance is rated at 100m. The front crystal and the caseback are sapphire. Steel versions use a ceramic bezel. The 26420CE version uses a black ceramic case.
Inside sits calibre 4401. It is an integrated chronograph, not a modular add-on. It uses a column wheel and a vertical clutch, it supports flyback, it beats at 28,800 vibrations per hour (4 Hz), and it stores 70 hours of power. The movement is visible through the back.
What the copies use
Most low-cost 26420 replicas use the ETA 7750 or a Chinese copy of it. That base runs at 28,800 vph, but its architecture differs from the 4401. The rotor and bridges are decorated to look like AP finishing, and the decoration does not match the real movement layout.
Top-tier builds use a clone of the 4401, made in China. Public sources do not agree on which workshop makes these movements, and no factory publishes production numbers. Claims of a 1:1 movement are marketing. A clone can copy the plate shape and the rotor, but it does not match AP finishing, part count or tolerances.
Where fakes show differences
Case and bezel
Measure the case. A real 26420 measures 43mm across the bezel. Copies listed at 43mm often measure 42.5mm or 43.5mm with calipers. Case thickness on the real watch sits near 14mm. Bezel screws on copies sit shallow, and the slot depth varies between the eight screws on a single watch. On the real watch the slots line up with the case and the polish breaks are sharp.
Dial and print
Look at the applied AP logo and the printing. On copies the letters sit thick, the spacing of the words drifts, and the print edge is soft under a loupe. The Tapisserie squares on a real dial are cut with sharp, uniform walls. Copy dials show rounded corners and a wider gap between squares.
Check the date. The 4401 has an instant-jump date. Copies show a slow creep across several hours, or a date disc that sits off-center in the window.
Chronograph behavior
Start, stop and reset the chronograph. The real flyback function restarts a running chronograph with one pusher press, with no stop and reset step. A 7750-based copy cannot do that. Pusher travel on copies is uneven, and the reset hand can land off zero.
Caseback and engraving
Real casebacks carry laser engraving with even depth on the reference number, the serial and the hallmarks. Copies show engraving with a bead-blasted look, or lines that do not line up with the case axis. A sapphire caseback also reveals the balance, the rotor and the column wheel. Real 4401 views show a blackened balance bridge, Geneva stripes and a gold rotor weight. Copies use rhodium plating and printed lettering.
Weight and feel
A steel 26420 on a rubber strap carries a set weight that changes with the strap and the clasp. A ceramic 26420CE feels lighter than steel. Ask the seller for a photo of the watch on a kitchen scale. If no weight is given, treat it as unknown data.
Price tiers
- Mid-tier: $250 to $450. 7750 base, mineral or sapphire crystal, plated movement decoration.
- Upper-mid: $450 to $650. Better case finishing, sapphire crystal, closer dial print.
- Top-tier: $650 to $900. Clone 4401, sapphire front and back, wider use of ceramic.
Genuine 26420 prices sit in the five-figure range. AP retail for steel versions is above $30,000, and black ceramic versions cost more. The price gap is the reason for the checks in this guide.
Checks before buying
- Ask for a movement photo through the caseback.
- Ask for caliper readings of case width and thickness.
- Ask for a weight photo on a scale.
- Ask for a video of chronograph start, stop and flyback reset.
- Ask for a macro shot of the dial print and the applied logo.
- Ask for a photo of the caseback engraving lit from one side.
What is not known
No public source lists the factory behind each 26420 case variant, and no factory publishes unit counts. Names used in the replica market change, and the same case can appear under more than one label. Treat any claim of an exact match to calibre 4401 as unverified.