On the front above are Gotic capitals , I think it is G_B ? Inside is engraved B_G .
May be there is another letter between them.

I can imagine that the local Arabic craftsman did not copy the capitals correct….….for him it are foreign signs in another language…..For us not all of these capitals are to read easily.
Perhaps the German soldier showed him his own ring with these Gotic capitals on it or he draw them on a paper as an example ?