The Fontainemelon 81-2 watch movement is an open face calibre with a Breguet hairspring. It features pallets and an impuls pin made of steel, provided it has 7 jewels. The specific differences between the calibres 7, 570 through 573, 670, and 671 are not known. The movement is part of a family of calibres with sizes ranging from 15.25 to 16.5''', and certain details of these calibres are only partially known. The Fontainemelon 81-2 movement functions include stem wind and set, as well as sub seconds. This movement was used around the period of 1930.