The Unitas 157 is an open face calibre movement that features a Breguet hairspring. It utilizes pallets and an impuls pin made of steel, with the option of 7 jewels. The differences between the 7, 570 through 573, 670, and 671 are not known. This movement is part of a series of calibres that share the same base, ranging from 15.25 to 16.5''', with only partially known details. Some of the other calibres in this series include 1, 510, 511, 515, 610, 611, 613, 1713, and 1815. Additionally, it is equipped with stem wind and set functions, as well as a sub-second feature. The Unitas 157 was commonly used around the period of 1930.