Seiko 4R36 caliber: dimensions and drop-in group

Used in: the branded day-date Seiko automatic, the retail version of the NH36.

The branded day-date Seiko at 27.40 mm x 5.32 mm that the NH36 copies. It shares the NH3x footprint and stem, so it drops into an NH36 case with a matching day-date dial.

Drop-in group: Seiko NH3x / 4R day-date footprint (27.40 mm x 5.32 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.