The 1st Royal Oak products were fitted with the calibre 2121 motion, which was determined by the calibre 2120 produced by Audemars Piguet in 1967, the planet’s thinnest self-winding movement of the period with day sign, and an Total peak of 3.05mm. The calibre 2121 was also Geared up using https://www.watchesworld.com/frozen-in-time-luxury-watches-for-winter/