Drop-in resolution
Miyota 9012 vs Seiko NH72 (TMI NH72A): do they swap?
Whether the Miyota 9012 and Seiko NH72 (TMI NH72A) share a case, and what changes if you move between them.
Different footprints. The Miyota 9012 is 26.00 mm x 3.90 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 9012 is a 90-series premium automatic with a 24-hour sub-hand and 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 (3.90 mm vs 5.32 mm), beat rate (28,800 A/h (4 Hz) vs 21,600 A/h (3 Hz)), calendar layout (centre seconds, date at 3, 24h sub-hand vs full skeleton, no date, hacking), winding behaviour. A 90-series slim automatic at 26.00 mm x 3.90 mm with date at 3 and a 24-hour sub-hand. It shares the 90-series footprint and dial feet with the 9015 but needs a dial with the 24h 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.