A fully gem set openwork perpetual calendar, reference 25659 was made in only 4 pieces over a 7 year period, from 1988 to 1995, 3 pieces in yellow gold and 1 piece in platinum.

The present Royal Oak Perpetual Calendar is an early version, with no leap year indicator and preserved in excellent overall condition. Cased in yellow gold with an exquisite diamond set finish this timepiece surely commands attention and prestige. Beyond its unquestionable rarity, the movement itself is a remarkable feat of engineering. Turn the watch over and you will witness genuine watchmaking artistry: a gracefully engraved and openworked main plate with floral and leaf scroll designs, as well as the Audemars Piguet emblem artfully rendered into the decor via the sapphire caseback. The outside section of the openworked dial is framed by the same pattern, which is visible through the case's cage. Immensely charismatic, its case proportions and diamond set finishing bedazzle the fortunate beholder. This timepiece on an intellectual level pushes the notion of a luxury sport's watch to its limits: the openwork can be considered a great show of complexity and the diamond-setting might be regarded the pinnacle of luxury. While such a contradiction is intellectually interesting, the execution is far from easy, however Audemars Piguet managed to integrate these two seemingly incompatible souls with style and panache. Remarkably, recent research has shown that only 3 examples in this particular configuration of yellow gold with diamonds were ever made.