Hi Dave
Up to a few weeks ago i would have said that their wasnt a german (25)Y fuze in exsistance, they were all (50)B Y , but i was shown a xray picture of a (25) Y taken sometime in 1940,s Clearly showing the marking (25) Y .
the first y fuze immunised by using liquid oxygen was carried out by Prof John Hudson, he still had the original fuze , which when we looked at it was actually a (50) B y of which i have several in the collection, john was as surprised as i was , it was he who produced the procedures for extracting these battery operated fuzes.
I have never actually seen a real (25) Y only (50)B y ,s