Drop-in resolution
Sellita SW290-1 vs Miyota 90S5: do they swap?
Whether the Sellita SW290-1 and Miyota 90S5 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Sellita SW290-1 (25.60 mm x 5.60 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 SW290-1 is the automatic small-seconds caliber with the sub-dial at 9, in dress and pilot watches. 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 (5.60 mm vs 3.90 mm), calendar layout (small seconds at 9, date at 3 vs open heart, no date). An automatic 11 1/2 ligne movement with small seconds at 9 and date at 3, at 25.60 mm x 5.60 mm. It shares the SW260-1 footprint but places the sub-seconds at 9, so each needs its own dial 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.