Built on Kurt Klaus’s groundbreaking crown-adjusted perpetual calendar architecture, this 18k rose gold Portugieser pairs full four-digit calendar complexity with a design engineered for everyday wear. It suits the seasoned collector seeking a perpetual calendar that can be adjusted with confidence, worn regularly, and appreciated for both its architectural ingenuity and refined execution.

Presents itself in mint condition with little to no signs of wear. Featuring a deep blue dial that shifts subtly under light, revealing layers of tone from every angle while keeping the calendar displays perfectly balanced and legible. Framing the dial is an 18k rose gold case that catches the light and emits a soft glow as it moves across the wrist. Bringing the composition together, the blue alligator strap adds texture and contrast, creating a seamless transition between the richness of the dial and the warmth of the case.

Functions include hours, minutes, perpetual calendar with date, day, month, four-digit year display, double moonphase, and seven-day power reserve. The crown on the right side of the case is used to set the time and advance the entire perpetual calendar system, allowing the date, day, month, year, and moonphase to move forward in complete synchronization without the need for additional pushers or tools. Because the calendar is fully integrated through Kurt Klaus’s crown-adjusted architecture, a single forward rotation advances all calendar indications together, reducing the risk of misalignment between displays. The automatic Calibre 52615 movement, powered by IWC’s Pellaton winding system, delivers up to a seven-day power reserve through natural wrist motion.

Comes as a full set, double-boxed, leather travel case, warranty card, operating instructions booklet, international limited warranty booklet, and original booklet sleeve.

Through its sapphire exhibition caseback, the Calibre 52615 is fully on display, appealing to collectors who value mechanical transparency and enjoy discussing the intricacies of high complication watchmaking. It belongs in the collection of someone who values not just visual refinement, but the depth of engineering.