Caliber reference
ETA / Unitas 6498-1 caliber: dimensions and drop-in group
The published footprint of the ETA / Unitas 6498-1 and which movements share it.
Used in: the small-seconds-at-6 sibling of the 6497-1, in large hand-wound wristwatches.
The same 36.60 mm x 4.50 mm large hand-wound caliber as the 6497-1, but with the small-seconds sub-dial at 6 rather than 9. The two share a case footprint but each needs a dial cut for its own seconds position.
Drop-in group: 16 1/2 ligne hand-wound, small seconds at 6 (36.60 mm x 4.50 mm). 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.