The Certina 15-21 watch movement is an automatic chronograph featuring a 60-second, 30-minute, and 12-hour counter function with a pillar wheel mechanism. It also includes a sub-second function. The day function can be set using a pusher at the 7:30 position. The date function allows for quickset adjustments. The month function is set via the date function. Additionally, the movement includes a moon phase complication which can be adjusted by using a pusher located at the 8 o'clock position. The Certina 15-21 movement was primarily used during the period of approximately 1970.