Drop-in resolution
Miyota 9075 vs Seiko NH34 (TMI NH34A): do they swap?
Whether the Miyota 9075 and Seiko NH34 (TMI NH34A) share a case, and what changes if you move between them.
Different footprints. The Miyota 9075 is 26.00 mm x 4.92 mm and the Seiko NH34 (TMI NH34A) is 27.40 mm x 5.32 mm, so they do not share a case. This is a choice between platforms, not a swap.
The Miyota 9075 is the Miyota true-GMT (traveller) automatic, in affordable GMT travel watches. The Seiko NH34 (TMI NH34A) is the affordable modding GMT automatic, adding a caller-GMT hand to the NH35 base.
They differ in diameter (26.00 mm vs 27.40 mm), height (4.92 mm vs 5.32 mm), beat rate (28,800 A/h (4 Hz) vs 21,600 A/h (3 Hz)), calendar layout (centre seconds, true GMT 24h hand, date at 3 vs centre seconds, GMT 24h hand, date at 3), winding behaviour. A 90-series-based true/traveller GMT at 26.00 mm x 4.92 mm with an independently-set local hour hand and a 24-hour GMT hand. Taller than the time-only 9015, it needs a GMT dial and hand set of its own.
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.