Audemars Piguet Royal Oak Openworked

Audemars Piguet has expanded its Royal Oak Openworked portfolio with two references that prioritize material metallurgy and chronometric architecture. The first, the 39mm Royal Oak "Jumbo" Extra-Thin Openworked (Ref. 16204XT), utilizes Grade 5 titanium alongside Bulk Metallic Glass (BMG). The second, the 37mm Royal Oak Double Balance Wheel Openworked (Ref. 15467BA), delivers the manufacturer's dual-oscillator escapement within a solid 18-carat yellow gold profile. These releases indicate a deliberate production shift toward monochromatic, tone-on-tone finishing that unifies the external case geometry with the structural framework of the calibers. Rather than relying on contrasting dial plates, the manufacture achieves legibility and visual depth purely through varied surface machining and targeted galvanic treatments on the movement components.

This strategy represents a significant divergence from traditional skeletonization, which historically prioritized excessive ornamentation and hand-engraved motifs. Modern openworking requires calculating the exact tolerances needed to remove maximum mass from the base plate and bridges without compromising the structural integrity of the gear train or the shock resistance of the escapement. For both the extra-thin Calibre 7124 and the highly kinetic Calibre 3132, CNC milling dictates the primary bridge layout before wire spark erosion removes the negative space. The resulting sharp interior angles are then individually beveled by hand using files and abrasive pastes, a process that dictates the low annual production volume for both references.

The Case and Dial

The 39mm x 8.1mm case of the Ref. 16204XT combines a standard titanium mid-case with a bezel and caseback milled from Bulk Metallic Glass. BMG is a palladium-heavy alloy, specifically marked as Pd500 on the caseback ring, cooled at a rapid rate during casting to prevent its atomic structure from crystallizing. This results in an amorphous metal matrix that possesses significantly higher hardness and scratch resistance than standard titanium, preventing the common denting often seen on the sharp octagonal edges of the Royal Oak bezel. Visually, the BMG bezel accepts a high-polish finish that yields a deep, almost liquid brilliance, contrasting heavily against the standard vertical brushing of the titanium lugs. The rhodium-toned openworked dial serves as a monochromatic extension of the case, featuring blackened 18-carat white gold hour markers and hands treated with luminescent material to provide stark focal points against the silver-grey inner bezel.

Conversely, the Ref. 15467BA relies entirely on 18-carat yellow gold for its 37mm x 10mm case, exploiting the dense, heavy properties of the traditional precious metal. The machining of solid gold requires entirely different feed rates and cutting speeds compared to titanium to prevent the metal from galling or tearing during the milling of the octagonal bezel and the integrated lug hoods. The finishing protocol remains strictly uniform, presenting aggressive vertical satin brushing across the flat surfaces that terminates cleanly into wide, mirror-polished chamfers running the length of the case flanks. The dial architecture is entirely yellow gold-toned, integrating seamlessly with the case, while legibility is maintained through the application of silver-grey luminescent hour-markers crafted from 18-carat pink gold and standard white gold hands. This lack of traditional contrasting dial colors forces the eye to focus strictly on the physical depth of the movement tiers and the shadow play generated by the skeletonized bridges.

The Movement Architecture

Powering the 39mm model is the selfwinding Calibre 7124, a highly optimized mechanism measuring just 29.6mm in diameter and an ultra-thin 2.7mm in height. Achieving this profile requires abandoning the traditional stacked arrangement of the gear train and mainspring barrel, forcing engineers to distribute the 211 components horizontally across a single plane. Operating at 4 Hz (28,800 vibrations per hour), the movement utilizes 31 jewels and delivers a guaranteed minimum power reserve of 57 hours. The open mainspring barrel located near the one o'clock position allows for direct visual confirmation of the mainspring's tension state. The movement finishing is executed in a uniform rhodium tone, displaying straight graining across the upper bridge surfaces and highly polished, hand-filed anglage on the numerous interior corners created by the skeletonization process.

The 37mm yellow gold model houses the selfwinding Calibre 3132, a radically different mechanism focused on chronometric stability rather than dimensional thinness. Measuring 26.6mm in diameter and 4.4mm thick, this 245-component movement operates at a lower frequency of 3 Hz (21,600 vph) with a 45-hour power reserve. Its defining feature is the patented double balance wheel mechanism, which places two balance wheels and two distinct hairsprings on a single balance staff. By linking these two regulating organs, the movement drastically increases its mass and moment of inertia, effectively self-correcting positional errors and minimizing the amplitude drop caused by sudden kinetic shocks to the wrist. The 38-jewel caliber is plated entirely in a warm gold tone, visually anchored by a skeletonized 22-carat gold oscillating weight mounted on ceramic ball bearings visible through the sapphire caseback.

The Bracelet and Integration

The integrated bracelet of the 16204XT titanium model incorporates BMG elements specifically at the intermediate linking studs. Utilizing this extremely hard, non-crystalline alloy for the pivot points directly addresses the mechanical wear and subsequent structural stretch that plagues older integrated designs subjected to daily friction. The bracelet tapers sharply from the lug hoods down to the titanium three-blade folding clasp, maintaining a continuous plane of vertical brushing across the primary links.

The solid 18-carat yellow gold bracelet on the 15467BA completely alters the physical dynamics and weight distribution of the 37mm case on the wrist. The strict machining tolerances between the links ensure structural rigidity, preventing lateral play while maintaining the necessary articulation to drape correctly over the wrist bone. Visually, the flanks of each primary link and the interior bevels of the connecting studs are mirror-polished, catching ambient light to define the geometric separation of the individual components before securing via the standard AP folding clasp.

Market Positioning and Availability

The 39mm Royal Oak "Jumbo" Extra-Thin Openworked in titanium and BMG is officially listed as Price on Request. This pricing strategy reflects the severe production bottlenecks associated with milling palladium-based metallic glass and the extensive hand-finishing required for the interior angles of the Calibre 7124. It operates entirely within the allocation-only tier of Audemars Piguet's catalog, targeting established clients focused on material innovation within the strict confines of the original 5402 case proportions.

The 37mm Royal Oak Double Balance Wheel Openworked carries a fixed retail price of $103,000. By deploying the complex dual-oscillator caliber in the smaller 37mm format, the manufacture successfully addresses the shifting collector preference toward sub-40mm case sizes without sacrificing mechanical density. Both timepieces are covered by a standard two-year guarantee against manufacturing defects, which is automatically extended to a five-year global warranty upon registration through the authorized retail network.

Technical Specifications

Case: 39 mm x 8.1 mm, Titanium with BMG bezel and caseback, glareproofed sapphire crystal, 50 m water resistance (Ref. 16204XT); 37 mm x 10 mm, 18-carat yellow gold, glareproofed sapphire crystal, 50 m water resistance (Ref. 15467BA)

Movement: Selfwinding Calibre 7124, 29.6 mm x 2.7 mm, 211 parts, 31 jewels, 4 Hz, 57-hour power reserve (Ref. 16204XT); Selfwinding Calibre 3132, 26.6 mm x 4.4 mm, 245 parts, 38 jewels, 3 Hz, 45-hour power reserve (Ref. 15467BA)

Dial: Rhodium-toned openworked, blackened 18-carat white gold hour-markers and hands (Ref. 16204XT); Yellow gold-toned openworked, silver-grey 18-carat pink gold hour-markers, white gold hands (Ref. 15467BA)

Strap: Titanium integrated bracelet with BMG studs and titanium folding clasp (Ref. 16204XT); 18-carat yellow gold integrated bracelet with AP folding clasp (Ref. 15467BA)

Price: Price on Request (Ref. 16204XT); $103,000 (Ref. 15467BA)

Reference Number: 16204XT.OO.1240XT.01; 15467BA.OO.1256BA.01

Notes: BMG (Bulk Metallic Glass) utilizes a palladium-based alloy (Pd500) for high scratch resistance; Calibre 3132 features a patented double balance wheel mechanism for increased rate stability.