Drop-in resolution
Sellita SW200-1 vs Miyota 90S5: do they swap?
Whether the Sellita SW200-1 and Miyota 90S5 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Sellita SW200-1 (25.60 mm x 4.60 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 SW200-1 is the primary Swiss alternative to the 2824-2, now the default in many microbrands. 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 (4.60 mm vs 3.90 mm), calendar layout (centre seconds, date at 3 vs open heart, no date). Matches the 2824-2 to the tenth of a millimetre in diameter and height, with the same date-at-3 layout, so it is the standard drop-in donor when a 2824-2 is unavailable. It carries one extra jewel (26 vs 25).
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.