Drop-in resolution
Sellita SW330-1 vs Sellita SW240-1: do they swap?
Whether the Sellita SW330-1 and Sellita SW240-1 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The Sellita SW330-1 (25.60 mm x 4.10 mm) and Sellita SW240-1 (25.60 mm x 4.60 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 SW330-1 is the Sellita caller-GMT automatic, the drop-in alternative to the ETA 2893-2. The Sellita SW240-1 is a Sellita automatic with small seconds at 6, in dress and field watches with a sub-dial.
They differ in height (4.10 mm vs 4.60 mm), calendar layout (centre seconds, GMT 24h hand, date at 3 vs small seconds at 6, date at 3). Built to the 2893-2 GMT footprint at 25.60 mm x 4.10 mm with a caller-style GMT hand and date at 3. It carries four more jewels than the ETA (25 vs 21) and is the standard donor when a 2893-2 is unavailable.
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.