Drop-in resolution
Miyota 8200 vs Seiko NH72 (TMI NH72A): do they swap?
Whether the Miyota 8200 and Seiko NH72 (TMI NH72A) share a case, and what changes if you move between them.
Different footprints. The Miyota 8200 is 26.00 mm x 5.67 mm and the Seiko NH72 (TMI NH72A) 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 8200 is the no-date base of the 8200 family, in clean-dial entry automatics. The Seiko NH72 (TMI NH72A) is the hacking, hand-winding skeleton member of the NH3x family.
They differ in diameter (26.00 mm vs 27.40 mm), height (5.67 mm vs 5.32 mm), calendar layout (centre seconds, no date vs full skeleton, no date, hacking), winding behaviour. The no-date base of the 8200 family at 26.00 mm x 5.67 mm, mechanically the 8215 without the date train. It shares the 8215 case footprint and drops into an 8200-series case cut for a no-date dial.
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.