The somewhat more recent models of the B & S are wonderful horns. I worked on a tenor for a client of mine a few years back. The top Bari player here in town plays on a horn from the newer stock. Unfortunately, they are no longer made.

Yours is an older version.

 I think it is referred to as the Blue Label, referring to the Blue B & S.

A similar look to the Black BC on the Buffet Crampon of the same timeframe.

Yours is probably an Eastern German example, made prior to the Wall Coming down and the unification of Germany. That is why the info seems somewhat hard to find.

It looks to be a nice horn with quite a few nice up to date modifications.

I have never had one in hand of this vintage.

The markings on the mouthpiece refer to the mouthpiece,

not the instrument itself.

Good Luck