The Bulova 12EBA watch movement is a detached manual wind movement. It is closely related to the Calma 508 calibre, although the connection between the two brands is uncertain. The movements in this family were produced at frequencies of either 18,000 or 21,600 A/h. The 558 movement is not documented in movement catalogs, and only models with a frequency of 21,600 A/h have been found. The reason for the variation in signature from HPP to HJP on certain samples remains unknown. Currently, no differences are known between the 451 and 461 variations. The Bulova 12EBA movement possesses the functions of automatic winding, a sweep second hand, and a date feature that can be adjusted by altering the time from 20-24 hours. It was predominantly utilized during the approximate period of 1970.