Drop-in resolution
ETA / Peseux 7001 vs ETA / Unitas 6497-1: do they swap?
Whether the ETA / Peseux 7001 and ETA / Unitas 6497-1 share a case, and what changes if you move between them.
Different footprints. The ETA / Peseux 7001 is 23.30 mm x 2.50 mm and the ETA / Unitas 6497-1 is 36.60 mm x 4.50 mm, so they do not share a case. This is a choice between platforms, not a swap.
The ETA / Peseux 7001 is the classic ultra-slim hand-wound caliber, in thin dress watches. The ETA / Unitas 6497-1 is the large pocket-watch caliber used in oversized hand-wound wristwatches.
They differ in diameter (23.30 mm vs 36.60 mm), height (2.50 mm vs 4.50 mm), beat rate (21,600 A/h (3 Hz) vs 18,000 A/h (2.5 Hz)), calendar layout (small seconds at 6, no date vs small seconds at 9). An ultra-slim hand-wound caliber at 23.30 mm x 2.50 mm with small seconds at 6. At just 2.50 mm tall it is one of the thinnest mechanical movements in wide use; its size is unique to the 7001, not shared with the 2800 family.
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.