Short answer
The reference 26420 is a 43 mm Royal Oak Offshore Selfwinding Chronograph, and it runs AP's in-house calibre 4404 — an integrated column-wheel chronograph with a 70-hour power reserve. It was also the first Offshore chronograph with a sapphire display back. That single design choice makes the reference unusually hard to copy well: the movement sits in plain view, and the distance between a 4404 and the generic chronograph bases used in replicas is not subtle once you get close.
What the reference 26420 actually is
AP introduced the 26420 in 2021 as the successor to the 44 mm 26400 Offshore chronographs, trimming the case to 43 mm while keeping the Offshore silhouette — octagonal bezel, exposed gasket, Méga Tapisserie dial. Steel, titanium, and gold versions all exist. The details that matter:
- Calibre 4404: integrated chronograph, column wheel, vertical clutch, flyback, 70-hour reserve, 4 Hz.
- 43 mm case with 100 m water resistance.
- Sapphire caseback, plus a sapphire crystal with anti-reflective treatment on both sides.
- Quick-release strap system — press the tabs, the strap comes off, no tools.
- Méga Tapisserie dial with the oversized grid pattern.
Where replica versions fall apart
The movement is the whole problem
Most replica Offshore chronographs run a modified third-party chronograph base — the familiar modular designs built around a common ébauche — dressed up with engraved plates, blued screws, and a rotor stamped to look like something it isn't. In a phone photo at an angle, that can pass. Under a loupe, or with the chronograph running, it won't. The pusher feel is mushy, the reset snaps instead of gliding, and the finishing is decorative rather than structural. Real 4404 finishing means hand-applied bevels, a blackened column wheel, and a free-sprung balance you can watch breathe.
Dial, date, and hands
The Méga Tapisserie squares on a genuine dial are sharply cut with consistent depth, and they catch light in a predictable way as you tilt the watch. On replicas the pattern looks soft, the spacing drifts near the date window, and the date font is wrong — too bold, badly centered, or sitting on a wheel that doesn't align flush with the printed text. Check the AP monogram at 12: the letters should be applied, not printed, and the spacing should square up with the numerals below.
Case, bracelet, and crystal
Offshore bracelets get chamfered and brushed by hand along every link edge. Replica bracelets show rounded, polished-over edges and a rattle you feel more than hear. The crystal is the other giveaway: genuine sapphire with double AR coating nearly vanishes at an angle, while replica crystals throw a blue-green cast and haze over the dial.
Caseback engraving
Reference numbers, serials, and the Swiss Made stamping are cut deep and crisp. Fakes use shallow etching with uneven letterforms, and the reference number often doesn't match the case metal or the dial configuration at all.
If you want the real thing
Buy from an AP boutique or a dealer with a documented service history, and ask for movement photos before you send money. Secondhand 26420s trade regularly, and a service record from AP is worth more than any seller's grading language. Budget for a service if the watch is more than a few years old.
"First copy" is a marketing term
Labels like first copy, 1:1, and super clone describe a seller's price tier, not a measurable quality standard. There is no factory producing a 26420 that a watchmaker would mistake for genuine, and importing counterfeit watches into the United States is illegal — U.S. Customs seizes them routinely. That's a practical risk, not a scare tactic.