Audemars Piguet Royal Oak Quantième Perpétuel Openworked Ref. 25829SP/O/0944SP/01 — Limited Edition 18/25, Full Set

Among the most compelling complicated Royal Oaks of the 1990s, reference 25829SP/O/0944SP/01 captures Audemars Piguet's mastery of both the perpetual calendar and the openworked tradition. Produced in just 25 examples to mark the 25th anniversary era of the Royal Oak, this highly exclusive steel-and-platinum edition combines technical sophistication with the restrained presence that defines the model at its best.

This example, numbered 18/25, presents the distinctive monochromatic bi-metal construction that makes the reference so attractive to collectors: a brushed steel case and bracelet set against polished platinum elements, including the bezel and centre links, creating a subtle richness without disturbing the architectural purity of the Royal Oak design. The sapphire dial reveals the openworked perpetual calendar mechanism in full, with indications for day, date, month, leap year, and moon phase arranged in the classical Royal Oak perpetual calendar layout.

Powering the watch is Audemars Piguet’s legendary selfwinding calibre 2120/2802, shown by AP Chronicles in its openworked 2120/2802SQ form for this reference. Developed as the successor to the maison’s earlier ultra-thin perpetual calendar movement, it added the leap-year indication and remained a cornerstone of the brand’s perpetual calendar production for nearly two decades. AP further notes that the openworking was executed in the traditional manner and that a single movement required approximately one month of skilled hand craftsmanship. 

The accompanying paperwork is especially important here. The original Audemars Piguet limitation certificate confirms reference 25829SP/O/0944SP/01, movement number 405593, case number D 86962, and serial number 18/25. The warranty booklet shows the same identifying numbers, calibre 2120/2802, and a retailer stamp from A. Seidich in Mönchengladbach, while AP Chronicles records this exact watch — no. 18/25 — as a 39 mm steel-and-platinum example sold in Germany in 1998.

For the discerning collector, this is not simply a rare Royal Oak. It is one of the defining openworked perpetual calendars of its generation: low-production, mechanically significant, visually unmistakable, and preserved with the kind of complete documentation that serious connoisseurs value most.

• Brand: Audemars Piguet
• Model: Royal Oak Quantième Perpétuel Openworked / Perpetual Calendar Openworked
• Reference: 25829SP/O/0944SP/01
• Limited edition: 18 of 25 pieces
• Case material: Steel and platinum
• Bracelet: Integrated steel and platinum bracelet
• Case size: 39 mm
• Dial: Sapphire openworked dial with grey subsidiary registers
• Movement: Selfwinding calibre 2120/2802, openworked form documented by AP as calibre 2120/2802SQ
• Functions: Hours, minutes, perpetual calendar, day, date, month, leap year, moon phase
• Movement number: 405593
• Case number: D 86962
• Provenance note: Sold in Germany in 1998
• Set: Full set
• Included: Wooden presentation box, manuals, Certificat d’Origine et de Garantie, Audemars Piguet limited-edition certificate signed by Georges-Henri Meylan