The Audemars Piguet Royal Oak Chronograph has seen many iterations and facelifts since its launch in 1997-1998 under reference 25860. Perhaps the most significant up until now took place in 2016 when the Royal Oak Chrono reference 26300 went from a 39 mm case to a 41 mm as reference 26320. Then in 2017, its dial was redesigned and reference 26331 replaced reference 26320. Back then, the hour and minute chrono registers were enlarged, the running seconds subdial was scaled down, shorter and wider applied markers were added and the typeface and transfers on the chronograph totalizers were updated.