Audemars Piguet’s Royal Oak collection is widely regarded as one of the most influential families in modern watchmaking. While the original 1972 release redefined the luxury sports watch with its octagonal case and integrated bracelet, subsequent references have deepened its technical and aesthetic impact. Among them, the Royal Oak Perpetual Calendar Ref. 25820SP.OO.0944SP.02 holds a unique place in the lineage, not only for its technical significance but also for its uncommon material pairing and distinctive visual character.

Unveiled in 1998 and produced until 2013, the reference 25820 marked the start of regular production for the Royal Oak Perpetual Calendar with a leap-year indicator. Its debut followed the 1995 anniversary release of the limited-edition Ref. 25810OR, which was the first Royal Oak Perpetual Calendar to reintroduce a leap-year display since the maison pioneered it in wristwatches back in 1955 with the Ref. 5516. The newly introduced Calibre 2120/2802 – an evolution of the ultra-thin automatic Calibre 2120/2800 that had powered Royal Oak Perpetual Calendar models since 1984 – enhanced functionality in the Ref. 25820 by incorporating a leap year indicator, shown via a hand mounted coaxially with the month hand.  

The 25820SP (S for steel, P for platinum) version of the reference stands out in the broader production run of approximately 1,235 pieces. Only 378 were made in this specific two-tone combination of stainless steel and platinum. Here, the utilitarian nature of brushed steel is paired with the refined brilliance of mirror-polished platinum, used on the bezel and centre links of the bracelet. The result is a distinctive configuration that departs from the Royal Oak’s characteristic mix of brushed surfaces and polished accents, replacing the customary brushed bezel top with a high-polish finish. In fact, the mirror finish on the platinum bezel (a feature typically reserved for only a few select models) slightly softens the sportier style of the watch, giving it a brighter, almost more formal approach.

The 39mm case diameter matches that of the original Royal Oak “Jumbo,” though the addition of the perpetual calendar complication, adds notable complexity to the dial. Rendered in deep black with the traditional Grande Tapisserie hobnail pattern, the dial of the 25820SP.OO.0944SP.02 is both legible and richly detailed. This tapisserie texture also marked a welcome return of Audemars Piguet’s signature pattern to the Royal Oak Perpetual Calendar line, as most earlier references were fitted with smooth dials.

A quartet of silvered subdials display the date (3 o’clock), moon phase (6 o’clock), day (9 o’clock), and month with leap year (12 o’clock), creating a bright contrast against the black background and visually tying back to the polished platinum bezel. Rather than the standard baton hour markers we’ve come to expect on Royal Oak watches, this version uses applied dots in white gold, further distinguishing it from more typical examples.  

The caseback reveals the self-winding Calibre 2120/2802 through a sapphire crystal window, showcasing Audemars Piguet’s exceptional finishing and mechanical finesse. The movement, which beats a 19,800 vibrations per hour and supplies around 40 hours of power reserve, retains the ultra-thin profile that makes the Royal Oak Perpetual Calendar remarkably slim for a complication watch. Notably, the 21k gold rotor in this version is treated with a dark finish, lending a modern edge to the otherwise traditional movement design.

The bracelet continues the theme of material contrast, using platinum for the polished centre links and steel for the rest of the structure. Interestingly, while the tops of the platinum links are polished to match the bezel, their undersides are brushed to align with the steel surfaces. It’s a subtle detail, but one that speaks to Audemars Piguet’s thoughtful approach to material interplay.

Produced in a variety of metal combinations, including yellow gold, rose gold, platinum, and tantalum, the 25820SP’s steel-and-platinum execution remains one of the most distinctive. It offers the everyday practicality of stainless steel, enhanced by the lustre, weight, and prestige of platinum. It’s a watch that feels elevated without appearing ostentatious.   

 

While newer perpetual calendar references have since entered the Audemars Piguet catalogue, the neo-vintage Royal Oak ref. 25820SP captures a transitional moment for the Le Brassus-based watchmaker. It was a period where technical milestones and adventurous design choices quietly converged.

Today, more than two decades after its debut, the Royal Oak Perpetual Calendar Ref. 25820SP remains a significant reference within the Audemars Piguet archives. It encapsulates the brand’s continued advancement of mechanical watchmaking within the context of the Royal Oak’s iconic design. From the gleam of its polished bezel and the clarity of its calendar display to the unexpected harmony of steel and platinum, the 25820SP reveals its appeal through quiet details. And it is precisely these subtleties that continue to resonate with discerning collectors and enthusiasts alike.