Drop-in resolution
Donor movement for the Seiko 4R36
Which movement drops into a Seiko 4R36 case, and what has to match beyond the footprint.
Drop-in available. The Seiko NH36 (TMI NH36A) shares the Seiko 4R36 footprint (27.40 mm x 5.32 mm, centre seconds, day and date at 3) and is the standard donor.
The Seiko 4R36 sits in the Seiko NH3x / 4R day-date footprint (27.40 mm x 5.32 mm) group. The Seiko NH36 (TMI NH36A) share its casing diameter, height and calendar layout, so a case and dial built for the Seiko 4R36 accept them with the correct dial and hands.
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.