An Audemars Piguet reference number has four blocks separated by dots: model and metal, gem setting, bracelet or strap, and dial. In 15510ST.OO.1320ST.06, 15510 is the 41 mm Royal Oak Selfwinding, ST means steel, OO means no gems, 1320ST is the steel bracelet, and 06 identifies the dial. Read it block by block and a long code becomes a plain description of the watch.
It is worth the two minutes. Royal Oak models look alike in small photographs, and the reference is often the only quick way to tell the generation, the metal and the dial. We have 655 Audemars Piguet watches in stock, including 329 Royal Oak models.
How to read an Audemars Piguet reference number
| Block | Example | What it tells you |
|---|---|---|
| 1 | 15510ST | Model number and case metal |
| 2 | OO | Gem setting |
| 3 | 1320ST | Bracelet or strap |
| 4 | 06 | Dial or version |
Block 1: the model and the metal
The five digits identify the model. A few that buyers meet most often:
| Model number | Watch |
|---|---|
| 15202, 16202 | Royal Oak "Jumbo" Extra-Thin, 39 mm |
| 15400, 15500, 15510 | Royal Oak Selfwinding, 41 mm, in three generations |
| 15450, 15550 | Royal Oak Selfwinding, 37 mm |
| 26331, 26240 | Royal Oak Chronograph, 41 mm |
| 26470, 26420 | Royal Oak Offshore Chronograph |
Higher numbers within a line are newer. The 15510, introduced in 2022, replaced the 15500, which had replaced the 15400. The differences are in the movement and in details of the dial, so the number tells you which generation you are looking at.
The two letters after the digits give the case metal:
| Letters | Metal |
|---|---|
| ST | Stainless steel |
| OR | Pink gold |
| BA | Yellow gold |
| BC | White gold |
| PT | Platinum |
| TI | Titanium |
| CE | Ceramic |
| SR | Steel and pink gold |
So 15510ST is the steel Royal Oak and 15510OR is the same watch in pink gold. This pair of letters explains most of the difference in price between two watches with the same model number.
Block 2: gem setting
The second block is usually OO, which means the watch is not set with gems. ZZ marks a gem-set watch. Other letter pairs exist for particular settings; when the second block is not OO, read the listing for the details.
Block 3: the bracelet or strap
The third block describes what the watch is worn on. It ends with letters that give the material:
- 1320ST or 1220ST: a steel bracelet. The bracelet's material matches the letters at the end, so 1320OR is a pink gold bracelet.
- Codes beginning with D or A and ending in CR or CA, such as D002CA or A600CA: a strap. CR stands for crocodile leather and CA for rubber (caoutchouc).
On the Royal Oak, this block tells you at once whether you are buying the watch on its integrated metal bracelet, which is how most buyers want it, or on a strap.
Block 4: the dial
The last two digits identify the dial or version. They are sequence numbers within a model. In the 41 mm Royal Oak 15510ST with a steel bracelet, for example, .06, .07, .08, .09 and .10 are five different dials of the same watch.
Because the numbers only make sense within one model, do not assume that 06 means the same color on a different watch. Use the photographs and the Dial line of the specifications to confirm the color.
Three references, read in full
15500ST.OO.1220ST.03 Royal Oak Selfwinding 41 mm of the previous generation (15500), steel (ST), no gems (OO), steel bracelet (1220ST), dial version 03.
26240ST.OO.1320ST.08 Royal Oak Chronograph 41 mm (26240), steel, no gems, steel bracelet, dial version 08.
26420SO.OO.A600CA.01 Royal Oak Offshore Chronograph (26420) with a case in two materials (SO), no gems, on a rubber strap (the code ends in CA), version 01.
We have 7 of the 15510ST.OO.1320ST.08 in stock, from $35,155.
Short and long forms
Sellers often shorten the reference to the first block: "15510ST" or just "15510". That is enough to identify the model and metal, and too little to identify the dial. Two watches listed as 15510ST can differ in dial color and in price. When it matters, ask for the full reference, or read it on the listing: every Audemars Piguet on our site shows the complete number.
Reference, case number and papers
Each Audemars Piguet also has an individual case number, engraved on the case back, and a movement number. Both are recorded on the warranty document together with the reference. When you buy, the reference on the papers should describe the watch in front of you, and the case number should match.
For older watches, Audemars Piguet offers an Extract from the Archives that confirms the original specification and date of sale.
Using the reference when you buy
- Read the model number to know the generation: 15400, 15500 or 15510.
- Read the metal letters next to it.
- Check block 3 for bracelet or strap.
- Match the last two digits when you compare prices.
For help choosing, see our Audemars Piguet buying guide, our Royal Oak price guide and our comparison of the Royal Oak and the Royal Oak Offshore. You can browse the Royal Oak and Royal Oak Offshore watches we have in stock.
Frequently asked questions
What does ST mean in an Audemars Piguet reference?
ST means stainless steel. OR is pink gold, BA yellow gold, BC white gold, PT platinum, TI titanium and CE ceramic.
What does OO mean in an Audemars Piguet reference?
OO in the second block means the watch is not set with gems. ZZ marks a gem-set watch.
What is the difference between the 15400, 15500 and 15510?
They are three generations of the 41 mm Royal Oak Selfwinding. The 15510, from 2022, is the current one; each generation brought a newer movement and changes to the dial.
What do the last two digits of an Audemars Piguet reference mean?
They identify the dial or version within that model. They are sequence numbers and do not mean the same thing on another model.
Where is the case number on a Royal Oak?
It is engraved on the case back, and it is recorded on the warranty document with the reference.
Is Watchflix NYC an official Audemars Piguet retailer?
No. We are an independent retailer and are not affiliated with Audemars Piguet. Every watch is checked by our specialist before it ships.
