Drop-in resolution
Seiko NH36 (TMI NH36A) vs Seiko 4R35: do they swap?
Whether the Seiko NH36 (TMI NH36A) and Seiko 4R35 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Seiko NH36 (TMI NH36A) (27.40 mm x 5.32 mm) and Seiko 4R35 (27.40 mm x 5.32 mm) are near in size but differ in height, dial feet or layout, so moving between them means a new dial, hands and often a case adjustment.
The Seiko NH36 (TMI NH36A) is the day-date sibling of the NH35, adding a weekday disc on the same footprint. The Seiko 4R35 is the branded Seiko date automatic behind many Presage and Prospex models.
They differ in calendar layout (centre seconds, day and date at 3 vs centre seconds, date at 3). Shares the NH35's 27.40 mm x 5.32 mm footprint and stem, so it drops into an NH35 case. The only change is the added day disc, which needs a dial with a day window and correct printing. It is the unbranded 4R36.
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.