Drop-in resolution
Sellita SW260-1 vs ETA 2893-2: do they swap?
Whether the Sellita SW260-1 and ETA 2893-2 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Sellita SW260-1 (25.60 mm x 5.60 mm) and ETA 2893-2 (25.60 mm x 4.10 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 SW260-1 is the automatic small-seconds caliber, in field and pilot watches with a sub-seconds dial at 6. The ETA 2893-2 is the GMT member of the 2892 family, base for many caller-GMT travel watches.
They differ in height (5.60 mm vs 4.10 mm), calendar layout (small seconds at 6, date at 3 vs centre seconds, GMT 24h hand, date at 3). An automatic 11 1/2 ligne movement with small seconds at 6 and date at 3, at 25.60 mm x 5.60 mm. Its sibling SW290-1 moves the sub-seconds to 9, so the two are not interchangeable without a matching dial.
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.