Jo â€” that is very useful.
Although my German is non-existent, it is quite clear that this material states that the piece is not by Walther.
I am somewhat bemused by this statement. I would be quite happy to accept that it does not appear in their surviving company archives and trade catalogues, and that therefore it is unlikely (but not impossible) to have been made and
marketed by Walther. That is quite fair. Making the leap to not being made by Walther seems to me illogical and unjustified without some other evidence.
I don't know of any major glassworks where we have perfect knowledge of what they did or didn't make.