Seiko 4R38

The 4R38 is an automatic movement manufactured by Seiko and belongs to the 4R caliber family. It is based on the 4R35 and retains the core specifications of that workhorse: 21600 vph frequency, 24 jewels, and approximately 41 hours of power reserve, with hacking and hand-winding functionality. The movement adds a day complication to the base 4R35's date feature, distinguishing it within the family. It remains in production and is used in Seiko 5 Sports and other entry-level Seiko models.