Short answer
The Royal Oak Offshore reference 26401 is the 44 mm chronograph line that debuted in 2014, most often seen as the 26401RO, 26401PO and 26401SR. It is one of the most photographed luxury chronographs made, which also makes it one of the most copied. Fake 26401 watches exist for nearly every dial colorway, and almost all of them fail on the same five points: case thickness, screw construction, movement finishing, dial texture and caseback engraving.
Counterfeits are illegal in most countries and cannot be serviced by the manufacturer. The steps below are for authenticating a watch you own, inherited or are being offered.
Reference facts to know first
- Case: 44 mm wide, about 14.4 mm thick, in steel, rose gold or platinum, with a rubber-clad crown and chronograph pushers.
- Movement: in-house caliber 3126/3840 automatic column-wheel chronograph, roughly 59 jewels.
- Dial: Mega Tapisserie grid texture, three subdials at 12, 6 and 9, date window at 3.
- Bezel: eight exposed hexagonal screws, ceramic or gold depending on the variant.
- Water resistance: 100 m.
What you need
- A 10x loupe, or a macro lens on a phone.
- A digital caliper, or the manufacturer's 14.4 mm thickness figure for comparison.
- Bright raking light and the watch flat on a table, not worn on a wrist.
How to authenticate a 26401
- Measure the case thickness. A genuine 26401 sits near 14.4 mm. Most replicas run 15.5 mm to 17 mm because the copied movement sits deeper in the case, so the profile looks inflated from the side.
- Examine the eight bezel screws. Each one must be a real threaded screw with a slot cut into the head, not a molded bump. Slot alignment is not a decorative pattern on the genuine watch.
- Read the dial print under a loupe. The AP monogram, the wordmark and the "Automatic" line should be sharp with no ink bleed. Fake Mega Tapisserie squares tend to be shallow with even spacing; the genuine grid has depth variation and a matte finish.
- Run the chronograph. On a genuine 3126/3840 the center seconds hand starts with a firm snap and the two subdial hands reset to zero at 12 and 6. Copy movements, often modified 7750 or quartz, give a soft start, a stuttering sweep or a loose reset.
- Inspect the date disc. The date window should be square-cut with beveled edges and the numeral centered in the aperture. Copies sit low in the window and use a stamped font.
- Turn the caseback over. Genuine engraving is deep, crisp and complete: reference number, case number, caliber number and Swiss Made. Replicas use shallow laser etching, wrong reference breaks, and often a caliber number that does not belong to a 26401.
- Study the movement through the display back. Look for Geneva stripes with even edges, blued screws and polished bevels on the bridges. Heat-stamped stripes or a plastic-looking finish mean it is a copy.
- Check the strap and buckle. Genuine rubber or alligator straps have a defined bevel, and the double-fold deployant is heavy with sharp clasp engraving.
- Confirm the serial. Ask for the extract from the archives or a service record from an authorized service center. No paperwork plus a mismatched case number is the strongest single signal.
- Get a second opinion. Any watch at this price deserves a hands-on check by a watchmaker who has opened a genuine 26401 before.
Frequent flaws in counterfeits of this reference
Thickness, screw construction, movement finish, dial texture and engraving depth on the caseback. The dial is the giveaway that shows in photos: copies read flat and uniform, while a genuine Mega Tapisserie catches light in uneven patches as the watch moves.
Quick takeaway
If a 26401 measures under 14 mm, has molded rather than threaded bezel screws, or a chronograph that starts soft, it is not genuine. Counterfeits of this reference are widespread, so buy only with service documentation and a professional inspection.