Drop-in resolution
Miyota 8217 vs Seiko NH72 (TMI NH72A): do they swap?
Whether the Miyota 8217 and Seiko NH72 (TMI NH72A) share a case, and what changes if you move between them.
Different footprints. The Miyota 8217 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 8217 is the 8200-family member adding a 24-hour indicator alongside the date. 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, 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 that adds a 24-hour sub-hand to the 8215's date layout. It shares the family footprint but needs a dial with the 24h sub-register.
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.