Calibre 3165 is a self-winding mechanical movement entirely developed and manufactured by Rolex. It features a Parachrom hairspring and Paraflex shock absorbers, offering greater resistance to shocks and to extreme conditions. Like all Rolex Perpetual movements, the 3165 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. Unusual for Rolex, the date on the caliber 3165 is displayed through a subdial at 3 o'clock.