Now then,i like that one Phil.
Ive been hanging on to see these pics before i nip out for a cheeky swift at the pub...
Ive never seen a fuze done in that way before mate.My guess would be that it is experimental and that the holes and letters are connected?
I reckon that you needed a special selector key to alter the timing perhaps?
The puzzle would be solved if one knew what the letters stood for?
I can only hazard a guess at the 'H' meaning 'Hoch'(high) so the fuze could be set for different height levels?,maybe the 'W' stood for 'Wasser'(water) use? Perhaps some of our german friends on here could help us out with this one?
Personally i reckon the letters stand for words that involve different heights?
So best guess is they were trying to make a multi-purpose fuze from a common impact like the 25?
best
waff