The Girard Perregaux 31.09 watch movement is an automatic mechanical movement utilized from 1966 onwards. It features a micro-rotor mechanism with four ball-bearings for enhanced performance. The Girocap combined settings mechanism is employed for the escapement wheel, contributing to improved precision. Additionally, the movement incorporates an indirectly driven minute hand, allowing for a low profile design. The movement further includes functions such as automatic winding and a date feature, which can be set by altering the 21-24 hour display.