Drop-in resolution
ETA / Unitas 6497-1 vs ETA / Unitas 6498-1: do they swap?
Whether the ETA / Unitas 6497-1 and ETA / Unitas 6498-1 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The ETA / Unitas 6497-1 (36.60 mm x 4.50 mm) and ETA / Unitas 6498-1 (36.60 mm x 4.50 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 ETA / Unitas 6497-1 is the large pocket-watch caliber used in oversized hand-wound wristwatches. The ETA / Unitas 6498-1 is the small-seconds-at-6 sibling of the 6497-1, in large hand-wound wristwatches.
They differ in calendar layout (small seconds at 9 vs small seconds at 6). A large 16 1/2 ligne hand-wound movement at 36.60 mm x 4.50 mm with small seconds at 9. It shares its size with the 6498-1, which differs only by placing the small seconds at 6, so the two are footprint twins but need their own dials.
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.