Drop-in resolution
Miyota 8245 vs Seiko NH72 (TMI NH72A): do they swap?
Whether the Miyota 8245 and Seiko NH72 (TMI NH72A) share a case, and what changes if you move between them.
Different footprints. The Miyota 8245 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 8245 is the fullest-calendar 8200 member, with day, date and a 24-hour indicator. 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, day and date at 3, 24h sub-hand vs full skeleton, no date, hacking), winding behaviour. An 8200-family caliber at 26.00 mm x 5.67 mm carrying day, date and a 24-hour sub-hand. It shares the family footprint with the 8205 and 8215 but needs a dial printed for its added complications.
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.