Audemars Piguet Royal Oak Perpetual Calendar Bleu Nuit

Audemars Piguet has introduced a new iteration of its Royal Oak Perpetual Calendar, Reference 26674CD.OO.1225CD.01, distinguished by the application of "Bleu Nuit, Nuage 50" ceramic for both the case and bracelet. This specific hue, historically associated with the dial of the original 1972 Royal Oak designed by Gérald Genta, has been translated into a ceramic material, marking a significant development in the manufacture's materials engineering. Alongside the aesthetic update, the timepiece debuts the Calibre 7138, a self-winding movement that integrates a patented "all-in-one" crown adjustment system. This mechanism eliminates the need for the traditional recessed correctors typically found on the case flanks of perpetual calendars, allowing the wearer to adjust all calendar indications via the crown alone. The release signals a continued focus by the Le Brassus manufacture on refining the user interface of high-complication horology while expanding its portfolio of colored ceramics.

The shift to a full ceramic construction in this specific colorway represents a complex challenge in materials science. Unlike standard black or white ceramics, which are relatively stable during the sintering process, obtaining a precise, saturated blue requires exact control over the chemical composition of the zirconium oxide powder and the firing temperatures. Pigments used to color ceramic are notoriously volatile under the extreme heat required for densification, often leading to inconsistencies in hue or structural integrity. By achieving the "Bleu Nuit, Nuage 50" tone—a deep, dark blue that mimics the appearance of a stormy sky—Audemars Piguet has managed to stabilize the color across the complex geometries of the Royal Oak case and bracelet components. The material offers a Vickers hardness rating significantly higher than the 316L steel or precious metals traditionally used in the Royal Oak line, providing substantial resistance to scratching and environmental wear, though it remains more brittle under direct high-impact force.

The Case and Dial

The case measures 41mm in diameter and maintains a profile thickness of 9.5mm, a dimension that preserves the wearability associated with the Royal Oak Perpetual Calendar line. The construction utilizes the aforementioned "Bleu Nuit, Nuage 50" ceramic for the bezel, case middle, and bracelet, while the caseback is rendered in titanium. This mix of materials serves a functional purpose; titanium’s hypoallergenic properties and lower thermal conductivity make it preferable for the component in direct contact with the skin. The case exhibits the signature finishing techniques of the manufacture, with alternating satin-brushed surfaces and polished chamfers. Achieving this level of finish on ceramic is considerably more labor-intensive than on metal, as the hardness of the material requires the use of diamond-tipped tools and extended polishing times to effect the same light-reflecting geometry without creating micro-fractures in the material. The case is rated for water resistance to 50 meters, sufficient for general daily use but distinct from the higher ratings found in the brand's Offshore diver variants.

The dial follows the traditional "Grande Tapisserie" pattern, a guilloché motif formed of raised squares cut by a pantograph engine. The color is color-matched to the case, creating a monochromatic aesthetic that emphasizes the legibility of the indications. The layout features the standard four-subdial configuration: months and leap year at 12 o'clock, date at 3 o'clock, astronomical moon phase at 6 o'clock, and day of the week at 9 o'clock. A central hand indicates the week number against a scale printed on the inner bezel, a feature relevant for business scheduling in European and international contexts. The hour markers and Royal Oak hands are crafted from 18-carat white gold and filled with luminescent material to ensure visibility in low-light conditions. The moon phase display uses a laser-ablated aventurine or sapphire disc to depict the astronomical moon, requiring correction only once every 122 years and 108 days, assuming the watch is kept wound. The integration of the blue inner bezel preserves the tonal uniformity, reducing visual clutter on a dial that conveys a high density of information.

The Movement

Powering the Reference 26674CD is the new self-winding Calibre 7138, a mechanism measuring 29.6mm in diameter and 4.1mm in thickness. Comprising 423 parts and 41 jewels, the movement operates at a frequency of 4 Hz (28,800 vibrations per hour). The 4 Hz frequency is a standard for modern precision timekeeping, offering a balance between component wear and rate stability against shocks. The movement provides a minimum guaranteed power reserve of 55 hours. While this reserve is lower than some simple three-hand movements, it is competitive within the realm of ultra-thin perpetual calendars, where the energy budget must account for the substantial torque required to drive the multiple calendar discs, particularly during the simultaneous turnover of date, day, month, and year indicators.

The most technically significant aspect of the Calibre 7138 is the crown-based adjustment system. In traditional perpetual calendars, the complex interaction of levers, cams, and stars necessitates the use of recessed pushers on the side of the case to advance individual indications. This traditional architecture presents a risk of water ingress and requires a stylus tool for operation. The Calibre 7138 incorporates a patented system that routes these corrections through the winding stem. This allows the user to adjust the week, day, date, moon, month, and leap year directly via the crown. Such a system requires a robust decoupling mechanism to prevent damage to the gear train if adjustments are attempted during the "danger zone"—typically between 10 PM and 2 AM—when the calendar gears are engaged for the daily change. The implementation of this user-interface improvement simplifies the ownership experience, removing the need for peripheral tools and maintaining the uninterrupted lines of the ceramic case flanks.

The Bracelet

The bracelet is an integrated unit crafted from the same "Bleu Nuit, Nuage 50" ceramic as the case. The production of a ceramic bracelet involves tight machining tolerances, as the individual links must articulate smoothly without the friction or grinding that can occur with ceramic-on-ceramic contact. Each link is individually finished with satin-brushing on the top surfaces and polishing on the edges, mirroring the case aesthetics. The bracelet is anchored by a titanium three-blade folding clasp. The use of titanium here is critical for mechanical reliability; the tensile strength and elasticity of titanium make it better suited for the repetitive stress of the locking mechanism compared to ceramic, which lacks elasticity and could fracture under the torsion applied during opening and closing.

Pricing and Availability

The Audemars Piguet Royal Oak Perpetual Calendar in "Bleu Nuit, Nuage 50" ceramic is listed as "Price on Request." This designation typically indicates a distribution model controlled strictly through the brand's boutique network, with allocation prioritized for established clients. The production volume is naturally limited by the yield rates of the colored ceramic components and the assembly time required for the Calibre 7138. The watch is positioned within the brand's high-complication sector, targeting collectors seeking technical novelty combined with material exclusivity.

Technical Specifications

Case: "Bleu Nuit, Nuage 50" ceramic; titanium caseback; 41mm diameter; 9.5mm thickness; water resistant to 50m.

Movement: Selfwinding Calibre 7138; 29.6mm diameter; 4.1mm thickness; 4Hz (28,800 vph) frequency; 55h power reserve; 423 parts; 41 jewels.

Dial: Blue Grande Tapisserie pattern; 18-carat white gold applied hour-markers and Royal Oak hands with luminescent coating; blue inner bezel.

Strap: Integrated "Bleu Nuit, Nuage 50" ceramic bracelet with titanium AP folding clasp.

Price: Price on Request

Reference Number: 26674CD.OO.1225CD.01

Notes: Features patented "all-in-one" crown adjustment system for calendar indications; no recessed correctors.