Audemars Piguet Royal Oak Perpetual Calendar Openworked “150th Anniversary”

Audemars Piguet recently commemorated its 150th anniversary with a special edition of the Royal Oak Perpetual Calendar Openworked. Limited to 150 pieces, this model is the last to house Calibre 5135, closing a chapter in the brand’s self-winding perpetual calendar lineage. The watch combines titanium and Bulk Metallic Glass (BMG) for a striking contrast against a dial design inspired by a historic pocket watch from the Musée Atelier Audemars Piguet (reference 25729). Special engravings and anniversary design elements distinguish this model, celebrating Audemars Piguet’s continued innovation in high watchmaking.

Since the 1970s, Audemars Piguet has played a pivotal role in advancing the perpetual calendar complication. At the height of the quartz crisis, the brand introduced Calibre 2120/2800, the thinnest selfwinding perpetual calendar movement of its time.

Calibre 2120/2800 made its way into the Royal Oak collection in 1984 with reference 5554, followed by an openworked version in 1986 (Model 25636). While wristwatch production grew, Audemars Piguet continued making classical and avant-garde pocket watches featuring the perpetual calendar. Building on this foundation, Calibre 5134 debuted in 2015, adapted for a 41mm Royal Oak case while maintaining a thin 4.5mm profile. This marked the return of the perpetual calendar to prominence, further solidified by the 2017 black ceramic edition (Ref. 26579CE), which became a key model in the collection.

In 2019, Audemars Piguet introduced Calibre 5135, combining traditional openworking with modern technology. The movement powered the Royal Oak Perpetual Calendar Openworked in black ceramic (Ref. 26585CE), showcasing the movement from both sides. Subsequent versions included an 18-carat white gold model set with 962 diamonds (Ref. 26625BC) and a collaboration with Cactus Jack (Ref. 26585CM) in 2023. The movement appeared again in a Frosted Gold version (Ref. 26585BC) in 2024.

Now, after nearly a decade of production, Calibre 5135 makes its final appearance in this 150th-anniversary edition, concluding its legacy in Audemars Piguet’s perpetual calendar line. This 41mm timepiece merges titanium with Bulk Metallic Glass (BMG), pushing material innovation further. Discovered in the 1960s, BMG is used in microelectronics, aerospace, and sports equipment, including golf clubs. When cooled rapidly, it prevents crystal formation, resulting in a glassy, amorphous structure with high wear and corrosion resistance.

Audemars Piguet developed a palladium-based BMG with over 50% palladium, providing durability and a glossy, mirror-like finish. The brand first introduced the material in the Royal Oak “Jumbo” Extra-Thin (Ref. 15202XT) for Only Watch 2021, marking the first use of palladium-based metallic glass in watchmaking. In 2023, BMG appeared in the Royal Oak “Jumbo” (Ref. 16202XT) before being integrated into a Royal Oak Perpetual Calendar (Ref. 26585XT) in 2024.

For this limited edition, BMG is used for the bezel, caseback frame, and bracelet studs. The material’s mirror-polished surfaces contrast with the titanium case and bracelet links, which feature a satin-brushed finish and polished chamfers. The result is a lightweight, shock-resistant timepiece with a refined play of textures and reflections.

To mark Audemars Piguet’s 150th anniversary, this model incorporates unique design details. On the dial side, the moon-phase display at 6 o’clock features a historically inspired “Audemars Piguet” signature, referencing early archival documents. The caseback frame includes two special engravings: a “150” anniversary logo and “1 of 150 pieces”, indicating the edition’s exclusivity.