Drop-in resolution
Miyota 9039 vs Miyota 9075: do they swap?
Whether the Miyota 9039 and Miyota 9075 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Miyota 9039 (26.00 mm x 3.90 mm) and Miyota 9075 (26.00 mm x 4.92 mm) are near in size but differ in height, dial feet or layout, so moving between them means a new dial, hands and often a case adjustment.
The Miyota 9039 is the no-date member of the 90 series, popular in clean-dial microbrand watches. The Miyota 9075 is the Miyota true-GMT (traveller) automatic, in affordable GMT travel watches.
They differ in height (3.90 mm vs 4.92 mm), calendar layout (centre seconds, no date vs centre seconds, true GMT 24h hand, date at 3). The no-date sibling of the 9015 at 26.00 mm x 3.90 mm, sharing the same dial-foot location. It drops into a 9015 case as long as the dial has no date window, which is its whole point.
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.