Seiko & Citizen Watch Forum Message Archive

Yes, the 7Sxx are clearlly derivated of the 70xx line of calibers. Almost a newer generation of 70xx calibers. But they have some differences that are sufficient to made Seiko change the name and not call them as "70something" calibers.

First, the base plate is quite different. On the 7S26, the keyless system was moved to the top side of the main plate, while the 7002 (and the whole 70xx line) have the keyless system on the bottom of the main plate, on the same side of the calendar. The keyless on the top side of the main plate is a very unusual solution, not only among Seiko. It may look as "not a big thing", but it is a big design modification. And that keyless was not simply "moved", but was completelly redesigned.

The calendar mechanism is different too. The difference is not only the fact of 7002 have just date, because the 7009 is the same 7002 but with a day/date calendar. The calendar mechanism of the 7S26 is completelly new. Not a big thing in my opinion, but is new.

And, of course, the jewels. The 7S26 (21j), compared to the 7002 (17j), gained 4 jewels (duh!). The 7002 didn't use any jewels for the 4th wheel, neither use Diafix. The 7S26 gained two jewels for the 4th wheel (an upper and a lower one), and the use of upper Diafix on both escape and 3rd wheels added 2 more jewels (one for each cap-jewel).

Regards,

Adriano