Audemars Piguet Royal Oak RD#2 Watch
It's not only the thinnest Selfwinding Perpetual calendar of any Royal Oak in production, at 6.30mm, it's also the thinnest in the world. The RD#2 from Audemars took five years to develop and is 30% thinner than anything currently in existence. This is achieved by combining the function of the perpetual three-level movement into a single, flat row of interacting components. The patented system boasts a tiny 2.89 mm central rotor; along with an attractive royal blue dial and a case, bezel, and bracelet composed of 950 platinum.