The little known Seiko 7s55 caliberWhen it comes to Seiko’s entry level automatic movements, most people will readily think of the well-liked and reliable 7s-caliber automatics that are found in the garden variety SKX and limited edition SKZ divers and of course, the popular Seiko 5 family of affordable watches.
The 7s26 is perhaps the most widely known movement in the 7s-family and is extensively used in the base line Seiko 5 model. The Seiko 5 Sports and Seiko 5 Superiors are adorned with the slightly upmarket 7s36 movement, which has 23 jewels – two more jewels than what the 7s26 has. Limited production run 7s-caliber divers such as the SKZ203K Yellow Monster and the SKZ201K Seiko 5 40th Anniversary diver’s watches also use the 7s36.
So what’s interesting about the 7s55?
The 7s55 appeared towards the later part of the 1990s and it was the shortest-lived member of the 7s family.
In essence, the 7s55 is mechanically similar to the date-only, 23-jeweled 7s35 caliber but fitted with a decorative “Tokyo Stripes” oscillating rotor with red inscription for aesthetic purposes. As with the other 7s family calibers, the 7s55 is a fully automatic movement, with no auxiliary hand winding or hacking feature and runs at the standard 21,600 beats per hour.
Unfortunately little is known about the history of the 7s55 movement as not many of them were made, compared to the mass produced 7s36. The bulk of 7s-caliber movements, prior to the end of 2006 were manufactured by the Seiko Instruments factory in, Singapore.
The 7s55 was never used in any other Seiko model and it wouldn’t have made sense for a decorated movement like that to be used in a solid caseback diver’s watch, where it cannot be seen.
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http://quartzimodo.com/the-little-known-seiko-7s55-caliber/)
