Citizen 6651A

The Citizen 6651A is an 8¾-ligne automatic movement featuring a micro-rotor with four ball-bearings, Parashock shock protection, and 21 jewels. Introduced between 1966 and 1970, it was the thinnest automatic movement of its era. The design incorporates a Girocap escapement and an indirectly driven minute hand, which enabled the notably low profile. Production has since been discontinued.