The Zenith 50.5 watch movement, produced from 1962 to 1969, was the first German electrical wrist-watch calibre. Featuring a electromechanically controlled balance motor, the movement was not self-starting, necessitating the lock of the balance in a position when the crown was pulled, ensuring reliable starting when pressed. Early samples lacked a regulator pointer. The M67 also offered a back crown, jumping sweep second, and an electrical and mechanical hack feature.