Drop-in resolution
Sellita SW220-1 vs Miyota 8215: do they swap?
Whether the Sellita SW220-1 and Miyota 8215 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Sellita SW220-1 (25.60 mm x 5.05 mm) and Miyota 8215 (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 Sellita SW220-1 is the Sellita day-date, the drop-in alternative to the ETA 2836-2. The Miyota 8215 is the low-cost Japanese workhorse, common in entry-level and fashion automatics.
They differ in diameter (25.60 mm vs 26.00 mm), height (5.05 mm vs 5.67 mm), beat rate (28,800 A/h (4 Hz) vs 21,600 A/h (3 Hz)), calendar layout (centre seconds, day and date at 3 vs centre seconds, date at 3), winding behaviour. The day-date member of the SW200 family, dimensionally matched to the ETA 2836-2 including the 5.05 mm height and day-and-date-at-3 layout.
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.