ETA 2824-2 caliber: dimensions and drop-in group

Used in: the reference Swiss workhorse automatic, used across mid-range Swiss brands for decades.

The dimensional benchmark for the whole 11 1/2 ligne core. Any donor claiming 2824 compatibility is measured against 25.60 mm x 4.60 mm with date at 3.

Drop-in group: 11 1/2 ligne automatic date (25.60 mm x 4.60 mm, date at 3). 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.