Audemars Piguet Royal Oak Perpetual Calendar 150th Anniversary Titanium — Sapphire Dial | Ref. 26585XT.OO.1220XT.01

Few anniversaries in watchmaking carry the weight of Audemars Piguet's 150th, and reference 26585XT.OO.1220XT.01 was conceived as an object worthy of that milestone. Produced in 2025, this Royal Oak Perpetual Calendar in grade 23 titanium pairs the manufacture's most intellectually demanding complication with a radical open-dial aesthetic — a sapphire crystal that dissolves the traditional face into pure transparency, allowing the perpetual calendar mechanism itself to become the centrepiece.

The movement within is Calibre 5135, a masterwork of miniaturised engineering housing 374 components across just 4.5mm of thickness, oscillating at 19,800 vph with 40 hours of power reserve. It displays week indication, day, date, astronomical moon phase, month and leap year simultaneously — a four-digit calendar requiring no manual correction until the year 2100. Blue counter surrounds echo the Royal Oak family's chromatic signature while matching inner bezel detailing and 18-carat white gold hour markers anchor the composition against the sapphire void.

The 41mm titanium case pairs with an integrated bracelet that innovatively combines bulk metallic glass (BMG) studs with titanium links — a materials engineering achievement that produces unparalleled smoothness against the wrist. Secured with an AP folding clasp and water resistant to 20 metres, the 26585XT is a limited-production anniversary edition priced at HKD 290,485. This is Royal Oak at its most architecturally daring: a perpetual calendar that wears its complexity openly, celebrating 150 years of Audemars Piguet's commitment to watchmaking that defies the ordinary.