Audemars Piguet Royal Oak Chronograph Ref. 26331ST

A latecomer to the Royal Oak

The Royal Oak arrived in 1972 as a steel sports watch sold at a luxury price, but it had no chronograph for a quarter century. The first chronograph to carry the Royal Oak name was the bulky Royal Oak Offshore of 1993, whose case was extended on the crown side to guard the pushers. A chronograph in the classic, slimmer Royal Oak line came only at the end of the decade. Most accounts, including one 2017 launch review, date it to 1997; a 2022 auction catalog note says 1998, and one collector's history splits the difference by saying it was announced in late 1997.

That first Royal Oak Chronograph, ref. 25860 in steel, measured 39mm across and used Calibre 2385, Audemars Piguet's name for the Frédéric Piguet 1185, one of the thinnest automatic chronograph movements ever made. The same history notes that the case was barely flared around the crown, far more subtle than the Offshore's wide guards.

The line then evolved in steps. In 2008 the case was rebuilt in three parts as ref. 26300. In 2012, the Royal Oak's 40th anniversary, the chronograph grew to 41mm as ref. 26320, with a wider-spaced 'Grande Tapisserie' dial, longer markers and a new butterfly clasp. Every one of these watches, through the 26331, used the same Calibre 2385.

Big eyes for a 20th birthday

Audemars Piguet unveiled the 26331 at the SIHH fair in Geneva in January 2017 to mark 20 years of the Royal Oak Chronograph. One launch review called it the chronograph's third facelift since 1997. The case stayed at 41mm and the movement stayed the same; almost all the change was on the dial.

The hour and minute counters at 9 and 3 o'clock grew larger, while the running-seconds subdial at 6 o'clock shrank. The hour markers became shorter and wider to hold more luminous material, the typeface and printing on the counters were updated, and even the counterweight of the chronograph seconds hand gained luminous paint. One collector's history adds that the AP signature was enlarged and the bracelet slightly reworked.

The biggest visual change was color. Instead of tone-on-tone counters, the steel versions got contrasting ones: rhodium-toned counters on the blue and black dials, and black counters on a silver-toned dial, the combination collectors call a 'panda.' A launch review said the two-tone dials were meant to appeal to a wider set of buyers who preferred contrast on a chronograph.

Underneath, Calibre 2385 carried on unchanged. The brand lists it at 26.2mm across and 5.5mm thick, with 304 parts, 37 jewels, a 3 Hz (21,600 vibrations per hour) beat and 40 hours of power reserve. It has a column wheel and a vertical clutch, and it sits behind a solid steel caseback. A 2017 review noted that Frédéric Piguet had by then become part of a Swatch Group brand and also supplied the 1185 to other watchmakers.

How to identify a 26331

Start with the subdials. The 26331 is the 41mm Royal Oak Chronograph with two large counters at 3 and 9 and a visibly smaller seconds subdial at 6. On the earlier 26320 the subdials are closer in size and colored to match the dial; on the later 26240 they are all the same size, set higher on the dial and, on most versions, colored to match.

Then find the date. Because the larger minute counter and the smaller seconds subdial needed even spacing, the date window moved clockwise and no longer sits centered between the 4 and 5 o'clock markers; one launch review complained about how close it sits to the 5 o'clock marker. Owners argued about it for years. When the 26240 arrived, some collectors welcomed a centered date and others said they preferred the 26331's.

Turn the watch over. A 26331 has a solid steel caseback. Its successor has a sapphire caseback showing the in-house movement.

In steel, the three standard references are 26331ST.OO.1220ST.01 (blue dial, rhodium-toned counters), .02 (black dial, rhodium-toned counters) and .03 (silver-toned dial, black counters and black outer zone). The same 26331 number also covered pink gold versions with blue or brown dials on bracelet or strap, a yellow gold version with a blue dial, frosted white gold, and a titanium-and-platinum 20th-anniversary edition, ref. 26331IP, with a slate grey dial and blue counters.

Sources disagree slightly on the case height. The brand and a 2023 auction catalog give 11mm, and a launch review measured it at 11mm against 10.8mm for the 26320, a difference the brand could not explain at the time. Another 2017 review gave the thickness as 10mm.

From $24,300 to the secondary market

At launch in 2017 every steel 26331 on bracelet listed at $24,300. Pink gold versions listed at $56,600 on a bracelet and $38,300 on an alligator strap, and the titanium-and-platinum anniversary model at $42,699. A price-tracking site recorded the steel retail price at about $36,100 by October 2021.

Watches from that run now change hands well above the original sticker. A black-dial example from about 2017, sold fresh to market by its original owner with its 2017 guarantee, brought $44,100 at auction in New York in December 2023 against an estimate of $20,000 to $40,000. A black-dial example from about 2021 had brought CHF 44,100 in Geneva in November 2022. In Hong Kong, a blue-dial example with extra straps sold online for HKD 302,400 in April 2025, and a black-dial example from about 2019, also from its original owner, sold online for HKD 304,800 in December 2025.

In May 2026 a blue-dial full set offered in a 24-hour online auction drew 18 bids and then sold by accepted offer for $43,900. At the end of September 2026 one price-tracking site estimated the pre-owned 26331ST at about $43,400, with the blue dial estimated highest and the black lowest.

Sources disagree on whether the 26331 is still made. A buyer's guide dates production of the steel 26331 to 2017 through 2022, and in early 2022 collectors were already describing the panda and reverse-panda dials as discontinued. Yet in October 2026 the brand's US website still listed all three steel references at $43,000 each.

The end of the Frédéric Piguet era

In January 2022, for the Royal Oak's 50th anniversary, Audemars Piguet put its in-house Calibre 4401 into a steel Royal Oak Chronograph for the first time, as ref. 26240. The new movement added a flyback function, and a launch review noted it was the first time a steel Royal Oak Chronograph had an in-house movement. The trade-off was thickness: the same review put the new case at 12.4mm, up 1.4mm from the 26331's 11mm. The 26240 started at $33,800 in steel.

Collectors noticed what had been lost as well. With the 26240 the brand moved to tone-on-tone dials, dropped the printed AP logo and thinned the bracelet. One owner of all three 41mm generations said he preferred the new watch's balance and display back; others said the 26331 was thinner, more legible, or simply better looking in panda. One forum member predicted that 'the pandas return back in 2027.'

That leaves the 26331 with a clear place in the story. It is the last generation of the 41mm steel Royal Oak Chronograph built on the Frédéric Piguet-derived Calibre 2385 with a solid caseback, and the last to offer contrasting panda and reverse-panda dials in steel before the switch to in-house movements.

The numbers

Reference

26331ST.OO.1220ST.01 (blue), .02 (black), .03 (silver-toned 'panda')

Caliber

Audemars Piguet 2385 (based on Frédéric Piguet 1185), self-winding column-wheel chronograph with vertical clutch, 26.2mm, 5.5mm thick, 304 parts, 37 jewels, 21,600 vph (3 Hz), 40-hour power reserve

Case

41mm stainless steel, 11mm per the brand (one review says 10mm), solid caseback, screw-locked crown, 50m

Dial

'Grande Tapisserie' with enlarged chronograph counters at 3 and 9, smaller seconds at 6, white gold applied markers, luminescent Royal Oak hands

Bracelet

Integrated stainless steel bracelet with AP folding clasp

Production

From January 2017; 2017 to 2022 per one buyer's guide; still listed by the brand in October 2026

Launch prices

$24,300 steel; $56,600 pink gold on bracelet; $38,300 pink gold on strap; $42,699 titanium and platinum

Timeline

1. 1972

   Audemars Piguet introduces the Royal Oak, a luxury steel sports watch.

2. 1993

   The Royal Oak Offshore becomes the first chronograph in the Royal Oak range.

3. 1997

   The first chronograph in the classic Royal Oak line, the 39mm ref. 25860, is launched with Calibre 2385 (a 2022 auction catalog dates it to 1998).

4. 2008

   The Royal Oak Chronograph case is redesigned in three parts as ref. 26300.

5. 2012

   For the Royal Oak's 40th anniversary, the chronograph grows to 41mm as ref. 26320.

6. Jan 2017

   The 26331 debuts at the SIHH fair in Geneva with larger contrasting counters, priced at $24,300 in steel.

7. 2017

   A titanium-and-platinum 20th-anniversary version, ref. 26331IP, is offered at $42,699.

8. 2019

   A smaller 38mm Royal Oak Chronograph, ref. 26315, joins the line alongside the 41mm 26331.

9. Oct 2021

   A price-tracking site records the steel 26331ST's retail price at about $36,100.

10. Jan 2022

    The 26240 brings the in-house flyback Calibre 4401 to the steel Royal Oak Chronograph, starting at $33,800.

11. Nov 7, 2022

    A black-dial 26331ST from about 2021 sells at auction in Geneva for CHF 44,100.

12. Dec 5, 2023

    A black-dial 26331ST from about 2017, from its original owner, sells at auction in New York for $44,100.

13. Apr 29, 2025

    A blue-dial 26331ST sells online in Hong Kong for HKD 302,400.

14. Dec 3, 2025

    A black-dial 26331ST from about 2019 sells online in Hong Kong for HKD 304,800.

15. May 29, 2026

    A blue-dial full set sells for $43,900 by accepted offer after a 24-hour online auction.

16. Oct 2026

    The brand's US website lists all three steel 26331ST references at $43,000.

The world in 2017

• Jan 21, 2017

  Millions of people worldwide join the Women's March, the day after Donald Trump's inauguration as US president.

• Mar 29, 2017

  The United Kingdom triggers Article 50, starting the Brexit negotiations.

• May 7, 2017

  Emmanuel Macron wins the French presidential election.

• Aug 17, 2017

  Scientists make the first observation of a collision of two neutron stars.

• Aug 21, 2017

  The 'Great American Eclipse,' a total solar eclipse, crosses the United States.

• Sep 15, 2017

  The Cassini spacecraft ends its 13-year mission by plunging into Saturn.

• Nov 15, 2017

  Leonardo da Vinci's 'Salvator Mundi' sells for $450 million at auction in New York, a record for any work of art.

• Nov 15, 2017

  Zimbabwe's military places President Robert Mugabe under house arrest.

Price record

A realized private sale is a completed transaction outside an auction room. The amount is what changed hands on the date shown. Private sales are reported less consistently than auction results, so a single comparable carries less weight than a run of them.

By reference price, Audemars Piguet Royal Oak Chronograph Ref. 26331ST is number 45 of 100 in the watches entries of the FLOAT 100. 54 of those 100 rest on a realized sale; the rest carry an asking price or a guide value, and each page says which. Rank within the FLOAT 100 itself (47 here) is editorial: how much an object defines its field, not price alone.

Did you know

• Every classic Royal Oak Chronograph from the first one through the 26331 used the same movement, Calibre 2385, based on the Frédéric Piguet 1185.
• The 26331's case came out 0.2mm thicker than its predecessor's with the same movement inside, and the brand could not explain the difference at launch.
• Even the counterweight of the 26331's chronograph seconds hand carries luminous paint.
• The off-center date window, pushed aside by the bigger counters, was one of the most argued-about details of the watch.
• Its in-house successor is 1.4mm thicker, which is why some owners still prefer the 26331.
• A 2017 black-dial example sold at auction in New York in 2023 for $44,100, more than its $40,000 high estimate.