Released in 1972 and designed by Gerald Genta, watchmaking's most famous designer, the Audemars Piguet Royal Oak was the first stainless steel luxury sports watch ever to exist. Released as a tactic to survive the quartz crisis, the Royal Oak can single-handedly be thanked for AP's existence today due to its success, albeit it wasn't an overnight hit. Its sizeable tonneau-shaped case, signature integrated bracelet, octagonal bezel, exposed screws, and steel construction failed to win over collectors until a few years later. Today, the Royal Oak is one of the most highly-coveted timepieces in all horology as its previously dismissed design details have permeated across the industry and into watches like the Patek Philippe Nautilus, Vacheron Constantin Overseas, Rolex Oysterquartz, amongst many other legendary timepieces.

The watch is in overall excellent condition. The case edges and profile remain well defined, with some scratches across the case and bracelet. The case back has some scratches but retains well-defined engravings. The bezel has some surface scratches and marks but remains well defined. The black petit tapisserie dial has aged to a pleasant chocolate hue. The hands are clean. The bracelet currently fits a 7 1/4" wrist and has 20 links, 6 of which are removable. The bracelet has minimal play between the links.

Made of stainless steel, the ref. 56175ST aided in popularizing the Royal Oak as it got collectors used to a luxury stainless steel timepiece from a brand like AP thanks to its smaller proportions and less expensive quartz movement.