Audemars Piguet Royal Oak Chronograph “50th Anniversary” Green Dial 41mm 26240ST. The Audemars Piguet Royal Oak Self-winding Chronograph “50th Anniversary” is a stunning watch that celebrates the 50th anniversary of the iconic Royal Oak collection. This timepiece features a 41mm stainless steel case, and a khaki green dial with three sub-dials. The watch comes on a stainless steel bracelet with an AP folding clasp. Model: Royal Oak Chronograph. Case Material: Stainless Steel. Bracelet Material: Stainless Steel. Box & Papers: Original box, original papers.