Seiko 7S36 caliber: dimensions and drop-in group

Used in: the extra-jewel sibling of the 7S26, in many Seiko 5 sports models.

A day-date automatic at 27.40 mm x 5.60 mm, the 7S26 with two more jewels and extra bracing. It shares the 27.40 mm NH3x case fit, so an NH36 is the usual hacking upgrade donor into a 7S36 case.

Drop-in group: Seiko 7S36 day-date footprint (27.40 mm x 5.60 mm). Matching diameter and height is necessary but not sufficient. A donor is only a true drop-in when the dial-foot positions, hand-hole sizes, stem length and calendar layout also match. Two movements can share a case and still need a new dial, re-broached hands or a cut-to-length stem.