This Audemars Piguet Royal Oak Perpetual Calendar, reference 26574ST, folds one of watchmaking's grand complications into the everyday language of a steel luxury sports watch, a proposition that keeps drawing collectors who want serious horology they can wear every day. Its self-winding Calibre 5134 was conceived expressly for the Royal Oak's slim proportions and drives a full perpetual calendar. The stainless steel case spans 41mm yet stands just 9.5mm thick, so a movement this complicated sits flat and unobtrusive on the wrist. A silver-toned dial with the Grande Tapisserie pattern and white gold markers keeps the reading crisp and the character restrained. Among the steel Royal Oak perpetuals, the silver variant remains the quieter, less often seen choice.