Drop-in resolution
Seiko NH36 (TMI NH36A) vs Miyota 9075: do they swap?
Whether the Seiko NH36 (TMI NH36A) and Miyota 9075 share a case, and what changes if you move between them.
Different footprints. The Seiko NH36 (TMI NH36A) is 27.40 mm x 5.32 mm and the Miyota 9075 is 26.00 mm x 4.92 mm, so they do not share a case. This is a choice between platforms, not a swap.
The Seiko NH36 (TMI NH36A) is the day-date sibling of the NH35, adding a weekday disc on the same footprint. The Miyota 9075 is the Miyota true-GMT (traveller) automatic, in affordable GMT travel watches.
They differ in diameter (27.40 mm vs 26.00 mm), height (5.32 mm vs 4.92 mm), beat rate (21,600 A/h (3 Hz) vs 28,800 A/h (4 Hz)), calendar layout (centre seconds, day and date at 3 vs centre seconds, true GMT 24h hand, date at 3), winding behaviour. 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.