This is a stainless steel Audemars Piguet Royal Oak 15400ST.OO.1220ST.01. It has a solid 41mm diameter three-body polished and brushed case on an integral stainless steel bracelet. 8 white gold screws secure the octagonal bezel and transparent sapphire crystal case back. The black dial has a grande tapisserie waffle decoration, luminous applied steel faceted baton index hour markers, luminous steel baton hands, and an outer track with second and minute divisions. The date aperture is at 3 o'clock and it has a screwed-down hexagonal winding crown. It's water resistant to 50 meters, and there is a 60-hour power reserve. The self-winding Audemars Piguet caliber 3120 movement is rhodium-plated with fausses cotes embellishment. It's constructed with 40 jewels, 280 components, a straight-line lever escapement, and a shock absorber mechanism. It has a suspended barrel, and the oscillating weight has an annular ring that runs on four jewels. It has a monometallic gyromax balance that's adjusted for heat, cold, and 5 positions. There is a self-compensating flat balance-spring, an engraved yellow gold rotor with a coat of arms, a variable inertia block balance, and a central hacking seconds mechanism. The 9.8mm thick case, dial, and movement are all signed. Jaeger-LeCoultre and Audemars Piguet produced the Royal Oak in 1972, with a custom Jaeger-LeCoultre movement. It was named for the British battleships of World War II, which in turn were named for the oak tree in which Charles II of England hid from his enemies, the Roundheads. The brilliant horologist Gerald Genta designed it. This steel-cased, luxury sports watch has become a signature line for Audemars Piguet. This watch is currently still being produced.