Drop-in resolution
ETA 955.112 vs Ronda 585: do they swap?
Whether the ETA 955.112 and Ronda 585 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The ETA 955.112 (25.60 mm x 3.15 mm) and Ronda 585 (25.60 mm x 3.60 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 955.112 is a common Swiss three-hand quartz caliber, the ETA rival to the Ronda 515. The Ronda 585 is a small-seconds Swiss quartz caliber, in dress quartz watches with a sub-seconds dial.
They differ in height (3.15 mm vs 3.60 mm), calendar layout (centre seconds, date at 3 vs small seconds at 6, date at 3), winding behaviour. A Swiss three-hand date quartz caliber at 25.60 mm x 3.15 mm sharing the 11 1/2 ligne diameter. It is not a mechanical donor: replacing an automatic with it changes power source and hand heights entirely. It competes with the Ronda 515 at the same diameter.
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.