The Bulova 6BL watch movement, manufactured by Alpina Gruen Gilde during the period 1929-1937, features an ingenious design where one simple part replaces the setting-lever spring, yoke, and yoke spring. The differences between the 575 and 762 versions are not known. Gruen lists two balance staffs and two lever arbors for the equivalent Gruen 179, suggesting the possibility of two Alpina calibres within the Alpina-Gruen Guild. The earlier Bulova 6BL movement bears the additional Gruen designation 179, indicating a likely finishing by Gruen, while the later Alpina 575 was purchased directly from Universal. Unfortunately, investigations regarding the movement are hindered by the fact that movement registers and staff lists only contain information about the base calibre Universal 259. The Bulova 6BL movement is a manual wind movement that includes a sub-second function.