Raimey,
thanks for all the new information.
Now that I have seen the 'double duck' for the first time clear in close up, it does look like a J and a Y

I could try and send that close-up photo to the Waffenmuseum Suhl, perhaps they have an answer
Would that be OK? (it's not my photo)

Best regards from England

Günter
NRA Life 1974