The Seiko 6138B watch movement, produced from 1962 onwards, features a micro rotor and is available in variations of 21 or 30 jewels, with a double jewel bearing. It incorporates a double excenter regulator for curb pins and stud carrier. The movement includes a self-winding gear with direction switching facilitated by a pinion floating between two large jewels. Notably, its indirectly driven minute and second hands allow for a low profile. Minor modifications to the base plate and simplified date driver were implemented around 1966-1967. The movement offers various functions such as automatic winding, sweep seconds, and a date feature that can be set by changing the 23-24 hour or 22-24 hour positions. It is also equipped with Incabloc shock protection.