Seiko movements family tree

The multitude of references in Seiko's history can be difficult to navigate. That's why I wanted to translate an excellent chart found in the book “Domestic Watch - Seiko Crown, Cronos, Marvel” by Yoshio Nagao & Yoshihiko Honda. This diagram is a sort of family tree of all Seiko's modern era manual-winding movements, from the 50s to the 70s.

After translating it, I thought it might be interesting to add a few automatic movements that were clearly the evolution of manual movements already present on the tree, so I might as well make the most of it. Then things escaladed quickly and I tried to make the tree as complete as possible, from the Marvel (1956) to the present day, concentrating solely on mechanical movements.

Of course, this work would never have been possible without the valuable information found in the book by Honda san and Nagao san, as well as in another book in the same series, “Domestic Watch - Seiko Automatic Updated Volume” by Mori Takeshi.

This diagram will need to be refined, corrected and completed, but this first version already covers almost every mechanical movement that has ever existed. Some movements, such as the 4S, have not been detailed in all existing versions.

One of the difficulties lies in the fact that Seiko changed its movement nomenclature in the early 60s from 3-digit to 4-digit. On the other hand, at that time, a movement corresponded to a particular range/name (e.g. cal.603 is exclusive to the Seikomatic), but over time, the same movement ended up in different ranges, and the same range may use several different types of movement. So you'll find both proper names (Marvel, Cronos, Skyliner etc) and movement references (cal. 6216, cal. 76 etc) or a mix of the two (Diver's 6105).

I hope that this huge amount of research, translation and formatting will be of use to the most ardent vintage enthusiasts, or at least help the curious to understand where certain modern movements come from.