Drop-in resolution
Sellita SW290-1 vs Miyota 9075: do they swap?
Whether the Sellita SW290-1 and Miyota 9075 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 9075 (26.00 mm x 4.92 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 9075 is the Miyota true-GMT (traveller) automatic, in affordable GMT travel watches.
They differ in diameter (25.60 mm vs 26.00 mm), height (5.60 mm vs 4.92 mm), calendar layout (small seconds at 9, date at 3 vs centre seconds, true GMT 24h hand, date at 3). 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.