The Audemars Piguet Royal Oak Perpetual Calendar Openworked 150th Anniversary reference 26585XT.OO.1220XT.01 is a highly exclusive 41mm timepiece released in 2025 to commemorate the brand’s sesquicentennial. This limited edition of 150 pieces features a multi-material construction, combining a titanium case middle and screw-locked crown with a bezel and caseback frame made from Bulk Metallic Glass (BMG). BMG is an amorphous palladium-based alloy known for its exceptional hardness, scratch resistance, and unique brilliance. The watch measures 9.9mm in thickness and maintains a water resistance of 20 meters. It is fitted with an integrated titanium bracelet that incorporates BMG studs and is secured by a three-blade AP folding clasp.
The timepiece is characterized by its openworked sapphire dial, which showcases the intricate mechanics of the self-winding Calibre 5135. The movement is composed of 374 parts, operates at a frequency of 2.75 Hz, and provides a 40-hour power reserve. Its complications include a perpetual calendar that displays the day, date, month, leap year, and week number, alongside an astronomical moon phase at the 6 o’clock position. The design utilizes a vintage-inspired aesthetic influenced by a historical 1992 pocket watch, featuring a blue inner bezel, blue counter surrounds, and a stylized cursive Audemars Piguet signature. Luminescent 18-carat white gold hour-markers and blue “bathtub” hands ensure legibility against the skeletonized movement.
General reviews of the 26585XT highlight its significance as the “swan song” for the Calibre 5135 movement series. Collectors and critics praise the innovative use of BMG and the high level of finishing on the openworked components, noting that the watch successfully bridges the brand’s historical roots with futuristic materials. While the aesthetic and technical craftsmanship are widely lauded, some enthusiasts point out that the 40-hour power reserve is relatively short for a modern perpetual calendar. Despite this, the watch is regarded as a premier collector’s piece due to its limited production, commemorative status, and the sophisticated evolution of its iconic Gerald Genta-inspired design.