The Bulova 5AB is an open face pocket watch movement available in options such as bimetallic screw balance and Breguet hairspring. It comes in sizes of 18.5 and 19''', with heights ranging from 4.2 to 5.9mm. There are different bridge layouts, two base plates with varying dial-feet positions, and two slightly different setting-lever springs. The assignment of these differences to specific groups and calibres like FHF 1 to 14 and FHF 1144, 2144, 2146, 4144, 4146 is partially known. The movement groups range from FHF 1 to FHF 16, with individual designations starting from FHF 22. The Bulova 5AB offers functions such as stem wind and set, sub second, and was commonly used around 1940.