The Elgin 556 is a mechanical watch movement that was produced from 1937 to 1970, with over 3.5 million units manufactured during this period. It features a manual-wind chronograph function, with a 60-second counter and 30/45-minute counters that are switched using a cam. The movement also includes a sub-seconds display and a date hand positioned at 6 o'clock. Due to the interchangeable nature of their parts, some series of this movement incorporated components from different calibers.