The Seiko Cal. 7S35 is a mainstream automatic movement with date produced by Seiko Instruments Inc. (SII). It was introduced in 2003 for a new line of mechanical Seiko watches, of which SNM001K was the first modern mechanical dress watch not called a Seiko 5. It was also used in the “Prince Monster” or “Landmonster” SNM series. Cal. 7S35 is very similar to Cal. 7S25 but with 23 jewels instead of 21, and Cal. 7S55 which is has a decorated rotor. It is also quite similar to Cal. 7S36, which adds a day wheel.
Cal. 7S35A was the original movement, produced from about 2005 through October 2006, when Cal. 7S35B was released. These feature updated parts on the balance staff, including an open-ended balance stud. It was further updated by 2011 to become Cal. 7S35C, the final version. This uses a different date disc and jumper, hour wheel, minute wheel, balance cock, ratchet wheel, first wheel, pawl lever, barrel and bridge, center wheel bridge and pinion, yoke spring, setting lever, and clutch wheel than versions A or B.
Cal. 7S55 is essentially similar to Cal. 7S35 except that it features finer finishing and was made in Japan rather than Singapore or Malaysia. Cal. 7S55 was used in the “Superior” SLX series watches with a display caseback. Cal. 7S55 was only produced in A and B versions.