Drop-in resolution
Miyota 8205 vs Miyota 8217: do they swap?
Whether the Miyota 8205 and Miyota 8217 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Miyota 8205 (26.00 mm x 5.67 mm) and Miyota 8217 (26.00 mm x 5.67 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 8205 is the day-date member of the 8200 family, with a weekday disc alongside the date. The Miyota 8217 is the 8200-family member adding a 24-hour indicator alongside the date.
They differ in calendar layout (centre seconds, day and date at 3 vs centre seconds, date at 3, 24h sub-hand). Shares the 8215 footprint at 26.00 mm x 5.67 mm but adds a day disc at 3, so it needs a dial with day and date windows. It swaps with an 8215 case only if the dial carries the extra 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.