Calibre 9001 is a self-winding mechanical movement entirely developed and manufactured by Rolex. Introduced in 2012, it is one of the most complex calibres ever created by Rolex watchmakers. Nonetheless, it is engineered to ensure simplicity of use: a selector wheel on the outside edge of the 9001 ensures the interaction of the movement and the bezel of the watch to set the Sky-Dweller’s functions. Like all Rolex Perpetual movements, the 9001 is a certified Swiss Chronometer, a designation reserved for high-precision watches that have successfully passed the Swiss Official Chronometer Testing Institute (COSC) tests. Its architecture, in common with all Oyster watch movements, makes it singularly reliable.