The tree can only find Jacob Blumberger, but the synagogue records seem to suggest there was a Jacob and a Joseph. And yet, that big donation article from 1905 has Jos. in one and Jac. in another.
Only one was a member, though, and if you look at all the syn. records labeled dues, they seem to use the names interchangeably.
Update: Joseph on one of the 3 versions of Alice's birth cert!