Current Seiko automatic movement families

[Der Amf]

I've been trying to get my head around the hierarchy of the various Seiko automatic movement families, and think I've got this right:

9S55
8L35 (lower spec 9S55)
4S15 (derived from 5200)
6R15 (derived from 7S26)
4R15 (lower spec 6R15)
7S26

Obviously each of those is just an example from its family and there are plenty of variations.

Aside from that, are there any other families in current production that I've missed? Have I got 8L and 4S the right way round? Do "S", "L" and "R" have any meaning?

Looking at the seeming jumble of letters and initial numbers, I can see that my confusion has been thoroughly reasonable.

[Wooster]

There's also the 6L35, which allows (again) for some thinner cases.

[Der Amf]

There's also the 6L35, which allows (again) for some thinner cases.

Googling that suggests (1) that it's an entirely new movement (2) that by being fitted to Presage watches, it should go just above the 6R15 in my list. Does that sound right?

edit: More googling says that it's actually derived from the 4L25, which had the same dimensions as the ETA 2892. This is an interesting read: https://musingsofawatchaddict.wordpr...-or-is-it/amp/

[Joe O'Brien]

9S55
8L35 (lower spec 9S55)
4S15 (derived from 5200)
6R15 (derived from 7S26)
4R15 (lower spec 6R15)
7S26

Obviously each of those is just an example from its family and there are plenty of variations.

Aside from that, are there any other families in current production that I've missed? Have I got 8L and 4S the right way round?

9S55 is actually the previous generation of GS movements, developed concurrently with the 8L as you noted. The current one is 9S65 which has the 3-day power reserve and the skeletonized 'MEMS' escapement. The current 8L35B is essentially a 9S55 upgraded with a 9S65 escapement.

You missed 4R35/6 which is actually not really related to 4R15 aside from the base architecture. 4R15 is a 6R15 without hacking or handwinding, but the 4R36 is basically a 7S26 with hacking and handwinding.

There's also the 6R20 family which is 4hz and consists of various layouts of power reserve, date and retrograde day subdials. Seiko would consider it higher than the 6R15 by virtue of being 4hz.

The 8R chronograph family is also 4hz, column wheel actuated and has a vertical clutch for each chronograph register. It's a module piggybacked onto a 6R2x base.

It's true that the 6L35 seems to be based on the 4L architecture, but we don't know anything about how much it's been changed or downgraded, aside from the obvious removal of Incabloc. It would indeed sit between 6R and 4S, anyway.

Do "S", "L" and "R" have any meaning?

If the letters have some specific internal meaning, I don't know what it is. In general you can use them to tell the position of the movement in the pecking order, but only in conjunction with the numbers. Typically the higher the first number is, the higher the movement is ranked, but of course that isn't true with the 7S or 4S. There's also a currently unused chronograph family called 6Sxx that was based on the 9S55, so that would be on the same quality level as 8L. In Grand Seiko, the letters tell you the type of movement - 9S denotes mechanical, whereas 9R would be Spring Drive. So it's hard to pin down what the letters mean.

Edit: 4S isn't actually used for any current-production models as far as I'm aware. It was last used in Credor, but I think the only mechanical family still being used in Credor is the 6830 (no letters! :p).