Answer
Reference 2561 is not listed in published Audemars Piguet Royal Oak reference charts. The documented line starts with the 5402 in 1972, then the 4100, the 14790, the 25594, the 25654, and the 25860. A listing that says "Royal Oak ref 2561" is using a seller number. Treat it as a label for a steel Royal Oak style watch with an integrated bracelet and a date at 3 o'clock, not as a factory reference.
What the number maps to
Most listings with this number show a 39 mm steel case, an octagonal bezel with eight hex screws, a tapisserie dial, and a taper bracelet. Those traits come from ref 5402ST. Published specs for the 5402ST list a 39 mm case, a thickness between 7.5 mm and 8.1 mm across the A, B, and C series, and caliber 2121. Caliber 2121 uses 36 jewels, runs at 19,800 vph, and carries a power reserve near 40 hours.
If a seller quotes other dimensions, ask for a photo of the watch on a caliper. Numbers on the page and numbers on the caliper differ in this market.
Case and dial checks
- Thickness. Genuine 5402 cases sit under 8.2 mm. Many replicas measure 9.5 mm to 11 mm.
- Bezel screws. Eight screws, each seated flush. On lower grades the slots point in eight directions and the hex edges show tool marks.
- Dial grid. The tapisserie squares on genuine dials are cut with a pantograph. Replica dials show printed lines with soft edges at 10x.
- Date window. The aperture edge is beveled and the date font matches the dial print. Replica date wheels use a wider font.
- Bracelet. End links meet the case with no step. Check the gap at the lug line.
Movements used in replicas
Three movement types appear. Entry builds use a quartz module. Mid builds use a Miyota 9015 or a Seagull automatic. Higher builds use a clone of the ETA 2824-2 with a decorated rotor and a bridge shaped like the 2121. No replica carries a genuine AP 2121. Ask for a movement photo with the caseback removed before payment.
Price bands and paperwork
Listed prices for these watches run from about US$120 to US$550. Sellers cluster near US$250 to US$400. Boxes and cards in that range are printed by the seller, not issued by Audemars Piguet. Serial numbers on the caseback do not match the AP archive. An extract from the factory will not return a ref 2561.
Legal status in the US
18 U.S.C. 2320 makes trafficking in counterfeit goods a federal crime. U.S. Customs and Border Protection seizes counterfeit watches at import. Buyers in the US carry a risk on delivery and on resale.