Drop-in resolution
Sellita SW215-1 vs Miyota 90S5: do they swap?
Whether the Sellita SW215-1 and Miyota 90S5 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Sellita SW215-1 (25.60 mm x 3.35 mm) and Miyota 90S5 (26.00 mm x 3.90 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 SW215-1 is the Sellita hand-wound with date, the drop-in alternative to the ETA 2804-2. The Miyota 90S5 is the open-heart member of the 90 series, showing the balance through the dial.
They differ in diameter (25.60 mm vs 26.00 mm), height (3.35 mm vs 3.90 mm), calendar layout (centre seconds, date at 3 vs open heart, no date), winding behaviour. The date-at-3 hand-wound member of the SW210 family at 25.60 mm x 3.35 mm, dimensionally matched to the ETA 2804-2. It is the direct manual-wind date donor.
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.