The Girard Perregaux 84.0 watch movement is an open face calibre, available with options such as a bimetallic screw balance and a Breguet hairspring. These pocketwatch calibres were manufactured in 18.5 and 19''', with heights ranging from 4.2 to 5.9mm. There are different bridge layouts, two base plates with varied dial-feet positions, and two slightly differing setting-lever springs. While the assignment of these differences to specific groups and calibres is only partially known, comparing the corresponding calibres provides some insight. The movement groups FHF 1 to 14 are designated by dimensions, with individual designations starting from FHF 22. The Girard Perregaux 84.0 movement features functions such as stem winding and setting, as well as a sub-second display. It was commonly used during the period around 1940.