The Elgin 336 watch movement is a hunter calibre mechanical movement introduced in 1914. It features a bimetallic screw balance with a riveted staff, and an optional monometallic screw balance with a press-fit staff. The movement is equipped with a Breguet hairspring, and in later samples, the setting-lever spring and click spring were modified. Occasionally, a smaller balance cock from the J17 movement may be used. Notably, the balance with a press-fit staff and the balance with a riveted staff are fully interchangeable with the hairspring. The J15 movement includes the functions of stem wind and set as well as a sub-second display.