The B is not always consistently a B, either, it changes shape and sizes. I think someone at some point had a Greek stamping set and some models I've seen have a B reminiscent of a the BETA symbol stamped into the shell, i.e. β

But that said, here are some samples off a few bikes I refurbed or restored over the years, both with B and Y stampings. Note the one with the utterly mangled Y (last pic), it came on a bike from Ireland I bought several years back.

Oh, and it seems the Romilly Sur Seine factory preferred stamping parallel to the BB lockring. Oh, and sometimes you'll find the serial stamped into the rear non-drive dropout.