Drop-in resolution
Miyota 90S5 vs Miyota 9019: do they swap?
Whether the Miyota 90S5 and Miyota 9019 share a case, and what changes if you move between them.
Same footprint, different calendar. The Miyota 90S5 and Miyota 9019 share the 26.00 mm x 3.90 mm case fit, but the Miyota 90S5 is open heart, no date and the Miyota 9019 is centre seconds, no date, slim, so a swap needs a dial cut for the new layout.
The Miyota 90S5 is the open-heart member of the 90 series, showing the balance through the dial. The Miyota 9019 is a slim no-date 90-series automatic, in clean-dial dress and field watches.
They differ in calendar layout (open heart, no date vs centre seconds, no date, slim). A 90 series caliber at 26.00 mm x 3.90 mm with an open-heart aperture that exposes the balance. It shares the 9015 footprint and dial feet but needs a dial cut for the open-heart window.
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.