Thanks for the additional scan, Ross. Using SG nomenclature...
OK, both stamps are definitely Die 1B. So the marking "DIE A" is in error. So...
0.5d stamp
-- the marking "N2" is correct, that is the correct type; but it is NOT Die A, but Die 1B
-- not good with colors, it looks like #324 "yellow green" to me; but SG doesn't list inverted watermark for that shade
***conclusion, it is #325Wi "bright green"
1d stamp
-- the marking "N11A" is incorrect; it should be N8 for #329Wi, or N9 for #332Wi
-- definitely Die 1B and not "DIE A"
-- not good with colors; it doesn't look like "scarlet" to me, but...
-- notice the clean cut perfs at right/bottom compared to the rougher "pulled perfs" at top and left; that indicates from a booklet...
-- which if I learned correctly, indicates that it must be #332Wi, as that stamp was the booklet stamp
***conclusion -- #332Wi
Subject to correction, of course...

k