Audemars Piguet, Royal Oak, ref. 26320OR.OO.D002CR.01, an 18 carat gold wrist watch, no. 4807, circa 2016, automatic chronograph movement, 37 jewels, cal. 2385, adjusted to heat-cold isochronism and 5 positions, black tapisserie dial, applied luminous baton markers, luminous baton hands, centre chronograph hand, subsidiary dials for constant seconds, 30 minute and 12 hour recording, date aperture between 4 and 5 o'clock, screwed down bezel and case back with eight screws, stamped with 18 carat gold common control mark, screw down crown and pushers, on an Audemars Piguet black leather strap with an 18 carat gold deployant clasp, case back, dial, movement, crown, strap and clasp signed, accompanied by an Audemars Piguet box, warranty, authentication and register certificate booklet, sealed instruction booklet and outer card packaging, diameter 41mm First produced in 1972, it took until 1998 for a chronograph to solve the intricacies of Gerald Genta’s case design and to join the Royal Oak line, leaving aside the over-sized ‘Offshore’ collection. The core range chronographs have all used the Cal. 2385 based on F. Piguet’s Cal. 1185 but this more modern iteration has grown from the original 39mm to a 41mm case.