Drop-in resolution
ETA 2824-2 vs Seiko NH35 (TMI NH35A): do they swap?
Whether the ETA 2824-2 and Seiko NH35 (TMI NH35A) share a case, and what changes if you move between them.
Different footprints. The ETA 2824-2 is 25.60 mm x 4.60 mm and the Seiko NH35 (TMI NH35A) is 27.40 mm x 5.32 mm, so they do not share a case. This is a choice between platforms, not a swap.
The ETA 2824-2 is the reference Swiss workhorse automatic, used across mid-range Swiss brands for decades. The Seiko NH35 (TMI NH35A) is the default modding and microbrand automatic, hacking and hand-winding at low cost.
They differ in diameter (25.60 mm vs 27.40 mm), height (4.60 mm vs 5.32 mm), beat rate (28,800 A/h (4 Hz) vs 21,600 A/h (3 Hz)), winding behaviour. 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.
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.