The fastest way to judge a watch sold as an "Audemars Piguet ref 16402" is to check the reference against AP's own catalogue, because 16402 does not appear in AP's published reference lists. The Royal Oak numbers it gets confused with are 5402, 15202, and 16202. I score any candidate on five points: documented reference, caseback engraving, movement architecture, dial execution, and price with provenance. The top pick among those checks is the caseback and movement pairing, since it is the hardest thing for a counterfeit to get right.

What the number 16402 actually means

Audemars Piguet built the Royal Oak Jumbo line under references 5402, then 15202, then 16202. No 16402 sits in that sequence, and AP does not list it as a production reference. A listing that leads with 16402 is usually a marketplace listing for a counterfeit, or a typo for 16202 that the seller is repeating without checking.

• Pro: a one-line catalogue check filters out most bad listings before you ever see photos.
• Pro: it costs nothing and needs no tools.
• Con: an incorrect reference does not by itself prove the watch is fake, since careless sellers copy mistakes from other listings.
• Con: some counterfeit listings use a correct-looking reference and hide the problem elsewhere.

Best for: the first pass on any listing, before you contact the seller or ask for more photos.

Check 1: caseback engraving and serial placement

On genuine Royal Oaks, caseback engraving is crisp and shallow, with even letter spacing and a clean transition where the flat back meets the case. Reference and serial numbers sit where the model calls for them, and the fonts match the era of the watch. Counterfeits show heavy, deep stamps that look pressed rather than cut, mismatched fonts between the reference and the brand name, and serials that would place the watch outside the production years for that reference.

• Pro: engraving quality is easy to judge from a sharp, straight-on photo.
• Pro: it exposes the mismatch between the reference on the listing and the reference on the watch.
• Con: polished or refinished cases can lose original engraving, so a soft stamp is not always proof of a fake.
• Con: a skilled counterfeiter can copy a real photograph of a real caseback.

Best for: narrowing a shortlist to two or three watches before you pay for professional inspection.

Check 2: movement architecture and finishing

Jumbo Royal Oaks from the 5402 and 15202 eras use a thin, historically correct automatic calibre, while later 16202 examples use a newer generation movement with a different bridge layout and a different rotor. Counterfeit watches often carry a stock or generic automatic movement under a decorated rotor plate, with Geneva stripes that stop short of the edges, missing perlage under the balance, and rotor text stamped instead of engraved. Ask for a clear movement photo with the caseback removed by a watchmaker, not a photo taken through the display back.

• Pro: movement layout is the strongest single tell, since tooling costs keep most counterfeit makers from copying it.
• Pro: a watchmaker can confirm it in minutes during a service estimate.
• Con: opening a watch voids some return policies and can damage a fragile case if done by the wrong hands.
• Con: parts from genuine movements do get swapped into counterfeit cases, so the movement alone is not the whole answer.

Best for: any purchase above a few hundred dollars, where the cost of a watchmaker's inspection is worth it.

Check 3: dial, hands, and bracelet finishing

The tapisserie dial pattern is cut, not printed, and the squares line up with the hour markers on a real watch. Counterfeit dials show a flat or printed texture, a date window with the wrong font or a visible ring around it, hands that are too thick or too polished at the edges, and a printed brand mark that sits slightly off centre. On the bracelet, look at the gap between links, the taper, and how the clasp closes. Genuine clasps close with an even snap and carry stamped, not etched, branding.

• Pro: these defects show up in ordinary product photos, with no special equipment.
• Pro: you can compare the dial directly against AP's own catalogue images.
• Con: aftermarket dials and refinished hands exist on otherwise genuine watches.
• Con: good lighting in a seller's photos hides texture and finishing problems.

Best for: remote buying, where you only have photos to work with.

Check 4: price and paperwork

A Royal Oak Jumbo in steel trades in the tens of thousands of dollars on the secondary market. A listing at a small fraction of that figure, with a reference that does not exist, is a counterfeit listing with a story attached. Genuine paperwork means a dated card or an archive extract from Audemars Piguet that states the reference, movement, and production date, plus a service history where available.

• Pro: price is the quickest reality check on any offer, real or fake.
• Pro: an archive extract confirms the reference directly with the manufacturer.
• Con: paperwork can be forged or borrowed from another watch.
• Con: paperwork does not travel with a watch forever, so a genuine watch can arrive without it.

Best for: final confirmation before money changes hands.

Legal note for US buyers

Trafficking in counterfeit goods is illegal in the United States, and buying one leaves you with no manufacturer support, no service path through Audemars Piguet, and no realistic resale route. A watch sold as a ref 16402 cannot be serviced or authenticated by the brand, and a jeweller who recognises it will not touch it. Treat any such offer as a counterfeit until the reference, caseback, and movement say otherwise.

Bottom line

Start with the reference. 16402 is not an Audemars Piguet number, so any watch described that way fails the first test. If a seller insists the watch is genuine, ask for the archive extract, a watchmaker's movement photo, and a straight-on caseback shot. If all three match a documented reference, you are looking at a real watch with a bad listing. If they do not, walk away.