The 12B was the flagship Bryston Preamp in the late'80's & early '90's before the Bryston BP-20 came on the scene.
I seem to recall it having a great MC Phono stage,as well as having a seperate Record/Listening feature,& having 2 AC outlets on the back pannel.
The build-quality was typical Bryston,which is to say it was excellent! The sound is more forward-sounding than the later Bryston Preamplifiers,(Like the BP-20),but still very enjoyable.
The price of the unit was around $1200.00 USD,so if you can score it at a great price,go for it!