Audemars Piguet launched their first Royal Oak Chronograph in 1998 via the ref. 25860 equipped with the self-winding cal. 2385 based off the cal. 1185 by Frederic Piguet. An important asset to the Royal Oak Chronograph the caliber was the thinnest self-winding chronograph movement ever made measuring a mere 5.5mm in thickness. Retaining its classic and slim profile of the original Royal Oak the ref. 26300 was released in 2008 replacing its predecessor. While its aesthetics may look very similar to the ref. 25830 the ref. 26300 features a case that was completely re-designed and rebuilt with a three-piece case similar construction as the case of the Offshore.