What do the 'a with caret/chevron' and 'a/aaa with cross-out' keys on Model F104, F122 and early M122 keyboards do?
For the keyboards' original terminal layout, the 'a with caret/chevron' key functions as an insert key and 'a/aaa with cross-out' functions as a delete key. Evidence for this can be found by examining the Model F-based IBM 3270 PC Keyboard Element (such as P/N 6110344
) - specifically, by comparing the physical layout
(credit to John Elliott) with a known functional layout diagram
(credit to John J. G. Savard).