The Seiko 5626B watch movement, introduced in 1956, is an automatic calibre operating at a frequency of 21,600 vibrations per hour. It shares similarities with the Eterna 1419U movement, but does not feature a ball bearing or gold rotor. Notably, it incorporates an indirectly driven minute allowing for a larger balance. The Seiko 5626B is part of a series of calibres, including manual wind options (2410, 2415, 2412, 2413, and 2417) operating at either 18,000 or 21,600 vibrations per hour.