The Audemars Piguet Royal Oak Perpetual Calendar Openworked (ref. 26585XT.OO.1220XT.01) was launched in 2025 to commemorate the maison’s 150th anniversary – a milestone marked by both technical finesse and material innovation. The openworked dial, set against the graphic geometry of the Royal Oak, provides a clear view of the final outing of calibre 5135, making this edition a fitting tribute to one of AP’s most refined calendar movements.

The 41mm case draws on a sophisticated blend of materials: a titanium midcase and screw-down crown are framed by a caseback and bezel made from Bulk Metallic Glass (BMG) – a zirconium-based alloy known for its high resistance to scratches and corrosion. The architectural skeleton dial exposes the perpetual calendar’s moonphase, week indication, and astronomical framework, powered by automatic calibre 5135 with a 40-hour power reserve. The watch is water-resistant to 20m and delivered on a matching titanium bracelet.

Produced in limited numbers and representing the swan song of calibre 5135, this anniversary edition stands as both a technical statement and a historic bookend, closing one chapter of Audemars Piguet’s perpetual calendar lineage in spectacular form.