ETA 2000-1 caliber: dimensions and drop-in group

Used in: a slim small automatic with date, common in ladies and mid-size watches.

A slim small automatic at 19.40 mm x 3.60 mm, thinner than the 2681. It shares the 2681's 19.40 mm diameter but at a lower height, so it is its own platform rather than a drop-in for the taller 2681.

Drop-in group: 8 3/4 ligne slim small automatic (19.40 mm x 3.60 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.