Audemars Piguet 26240ST Royal Oak Chronograph "50th Anniversary" SS Blue Dial

This Audemars Piguet Royal Oak Chronograph reference 26240ST.OO.1320ST.01 marks the 50th anniversary generation of the model. Its self-winding caliber 4401 brought the line fully in-house, replacing the outsourced bases that had powered earlier Royal Oak Chronographs and giving this watch a different place in the family's development. The flyback chronograph is the point here, not the date tucked beside it, and for a collector following how Audemars Piguet updated its modern staples this is the reference where that shift becomes visible. In stainless steel, the case measures 41mm across and 12.4mm thick, a size that keeps the Royal Oak's familiar stance without pushing it out of proportion. The blue dial is the signature pairing for the steel chronograph, and in this anniversary series it ties the watch directly to one of the model's most established modern configurations. More than a cosmetic refresh, this reference shows Audemars Piguet bringing one of its central sports watches onto its own mechanical footing.