Drop-in resolution
ETA 2804-2 vs ETA 2893-2: do they swap?
Whether the ETA 2804-2 and ETA 2893-2 share a case, and what changes if you move between them.
Close in diameter, not a drop-in. The ETA 2804-2 (25.60 mm x 3.35 mm) and ETA 2893-2 (25.60 mm x 4.10 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 2804-2 is the hand-wound date member of the 2800 family, the manual sibling of the 2824-2. The ETA 2893-2 is the GMT member of the 2892 family, base for many caller-GMT travel watches.
They differ in height (3.35 mm vs 4.10 mm), calendar layout (centre seconds, date at 3 vs centre seconds, GMT 24h hand, date at 3), winding behaviour. The manual-wind, date-at-3 version of the 2800 family at 25.60 mm x 3.35 mm. It adds a date disc to the 2801-2, so it needs a dial with a date window and swaps with the Sellita SW215-1.
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.