The Seiko 6600-7100 watch movement is a mechanical movement that was used during the period of 1964-1972. It was particularly designed for the Ocean Star model and features a lever to release the stem from the dial side. The movement's finish, including the rotor, cannot be linked to its production date. Early samples of the movement still have the split stem of its predecessor, requiring the date to be set by changing between 20 and 24 hours as the stem cannot be pressed in deep enough. The crown section of this stem cannot be pulled off and the movement drops out of the front of the case when the stem is turned to leave the T-gap. The minute wheel and cannon pinion are positioned between the plates, with only their bearings visible. Removing the bridges grants access to the minute wheel, which is driven by the barrel through the over gear, and the friction-coupled cannon pinion drives the hands gear. The section with the notch for friction is relatively short, making it challenging to narrow it for improved friction. The Reed's regulator screw has holes in its head, allowing for precise adjustment without risking damage to the balance or hairspring.