The perpetual calendar undoubtedly constitutes a pivotal chapter in Audemars Piguet’s history, a tradition of horological complication that the Royal Oak collection has elegantly upheld since 1984. Now, the debut of the Royal Oak Selfwinding Openworked Perpetual Calendar—powered by the brand-new Calibre 7139—marks yet another innovative breakthrough in Audemars Piguet’s technical mastery. Unveiled alongside the equally exquisite Code 11.59 collection, this timepiece serves as an even more vivid embodiment of the very essence of Audemars Piguet’s style. Truth be told, if given the choice, most people would likely opt for the Royal Oak without a moment's hesitation.

The Audemars Piguet Royal Oak Perpetual Calendar Openworked watch features a 41mm diameter and a thickness of just 9.5mm, boasting perfectly balanced proportions and an exceptional tactile feel. Compared to previous openworked perpetual calendar models, it appears notably slimmer, and its wearing comfort has been significantly enhanced. The case is crafted from lightweight titanium, while the bezel, caseback, and bracelet studs incorporate AP’s exclusive BMG (Bulk Metallic Glass) material—a substance previously utilized in the Royal Oak 150th Anniversary Perpetual Calendar timepiece. The satin-brushed finish of the titanium intertwines with the mirror-polished BMG to create a mesmerizing interplay of light and shadow that flows like water—a design at once exquisitely refined and imbued with a sense of modern technological sophistication.

The integrated bracelet, paired with a slimmer profile, ensures the timepiece sits snugly and securely on the wrist. Adorned with BMG pins, the titanium bracelet feels both lightweight and fluid—a testament to exquisite craftsmanship—while its alternating brushed and polished surfaces perfectly echo the finish of the watch case. In actual wear, one senses its substantial, solid quality without ever feeling weighed down; it feels less like a delicate heirloom requiring cautious handling, and more like a trustworthy "technical partner." Its 50-meter water resistance further reinforces this philosophy: this is a perpetual calendar designed to be a daily companion, rather than merely a masterpiece to be admired from within a display case.

The dial layout adheres to a clear functional segmentation: the day of the week and 24-hour indicator are positioned at 9 o'clock; the date at 12 o'clock; the month and leap-year cycle at 3 o'clock; and the moon phase display at 6 o'clock. The days of the week are printed on the sloped inner bezel, a clever utilization of space. In fact—aside from the hours and minutes indicated by the lume-filled rose gold hands—the current day of the week is the most instantly legible feature, thanks to a white central pointer that stands out vividly against the dark bezel. As for the other calendar indications, the small rose gold sub-hands may appear somewhat intricate at first glance; however, a simple flick of the wrist—allowing the light to catch the dial at just the right angle—brings them into sharp, effortless focus. Overall, the dial exudes a sense of calm composure amidst its complexity, avoiding any visual clutter or overwhelming aesthetic.

The Calibre 7139, which powers the Audemars Piguet Royal Oak Perpetual Calendar Openworked, is an openworked upgrade of last year’s Calibre 7138. Based on the Royal Oak Jumbo Ultra-Thin automatic Calibre 7121, it integrates all perpetual calendar functions into a single-layer movement, incorporating numerous R&D innovations from the brand. The movement measures just 4.1 mm in thickness, beats at a frequency of 28,800 vibrations per hour, and offers a power reserve of 55 hours.