Why yellow gold, you might ask — a material that has in recent years fallen out of vogue in the watch aficionado community. Like the most recent models of the Royal Oak Perpetual Calendar, in steel and rose gold .

This watch has a 41-mm case in the classical octagonal style of the Royal Oak collection and featuring a clear, glareproof sapphire caseback. It has a screw-locked crown, ensuring water-resistance of 20 meters.

The blue dial is decorated with the collection’s familiar “Grande Tapisserie” pattern of subtly raised three-dimensional squares. The calendar displays are on prominent subdials at 9 o’clock , 12 o’clock , and 3 o’clock . In addition, an astronomical moon-phase display appears at 6 o’clock and the week of the year is indicated on a numbered 1-52 chapter ring surrounding the dial. The applied hour markers, like the case, are in yellow gold and the hands are treated with luminous coating.

Also like its predecessors, which debuted earlier this year, the Audemars Piguet Royal Oak Perpetual Calendar in yellow gold contains a new movement, the self-winding Caliber 5134, based on AP’s Caliber 2120.

It consists of 374 parts, including 38 jewels, measures 29 mm in diameter by 4.31 mm thick, and has a balance frequency of 19,800 vph (2.75 Hz). According to Audemars Piguet, the movement carries a minimal guaranteed power reserve of 40 hours.

The yellow gold version of the Audemars Piguet Royal Oak Perpetual Calendar case with an 18k yellow gold bracelet