The Hamilton 15 watch movement features a rotor placed out of center and integrates the winding gear within the movement, resulting in a remarkably thin design for its time. It utilizes a detached manual wind mechanism and is equipped with a screw balance, later replaced by a ring balance. The split stem for Ocean Star models is not detachable by pulling the crown; it detaches when the movement drops out of the case after turning the crown to the correct angle. The movement includes automatic winding and sweep seconds, and incorporates a date function that can be set by changing the 20-24h range. The Hamilton 15 movement was in use around 1963.