Nigel...the first bassman amps were only available with 4 10's. They looked like a super, with controls on the back horizontal panel. They were open back...darker brown cover. I don't know when bassman amps were redesigned. The other one I have is a 1976 bassman 50...at least that's when I bought it. It has a chrome plate (not blackface) and black covering. The cabinet has two 15's that are mounted diagonally.The next generation of Fender amps I saw after the dark brown bassman were blond cabinets and separate heads and cabinets.

Russ