Years ago, I got terribly confused by Dartington marks
always looking like Bs.
So when somebody says something is marked with a B, the automatic response - especially for a rather solid or substantial clear piece of glass, is... Dartingtion!
Reidel is another company that can have very confusing marks which look like letters they're not.
I'm sure we'll be able to find out what it is, eventually. There are loads of other folk here, and we don't all come along every day. But we don't give up, Nathan.

Ever.