Drop-in resolution
ETA 2801-2 vs Sellita SW210-1: do they swap?
Whether the ETA 2801-2 and Sellita SW210-1 share a case, and what changes if you move between them.
Interchangeable. The ETA 2801-2 and Sellita SW210-1 share the same 25.60 mm x 3.35 mm footprint and the same centre seconds, no date layout, so one drops into the other's case with the correct dial and hands.
The ETA 2801-2 is the hand-wound, time-only member of the 2800 family, in slim dress watches. The Sellita SW210-1 is the Sellita hand-wound, the drop-in alternative to the ETA 2801-2.
Their published figures are the same to the tenth of a millimetre. The manual, no-date base of the 2800 family at 25.60 mm x 3.35 mm. It shares the family diameter but has no rotor and no calendar, so it swaps only with the Sellita SW210-1 hand-wound caliber.
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.