The Fontainemelon 73-2 watch movement, which was produced between the years 1916 and 1930, is a notable open face calibre designed and manufactured by LePhare and Zenith. This movement incorporates details outlined in the Swiss Zenith patent 62623. It features a bimetallic screw balance and utilizes a Breguet hairspring. The movement also includes several functions, namely a stem wind and pin set alarm, as well as a sub-second feature. The quantity of Fontainemelon 73-2 movements manufactured is estimated between 5000 and 6000, depending on the source, with equivalent LePhare models available, albeit lacking the typical Zenith balance cock.