The Audemars Piguet Royal Oak Selfwinding Tanzanite "50ᵀᴴ Anniversary" 41mm (ref. 15514BC.TF.1284BC.01) is an automatic sport watch, with a 41mm 18-carat white gold case, powered by the 4309 movement and a 70-hour power reserve. Water resistance is rated to 20m, under a sapphire crystal.