Yes - the AC30 (both early types) were available in 1961.
The book "The Shadows - By Themselves" (op cit) mentions the top-boost unit in the back of the amp. That would be the mainstream 6-input, 3-channel AC30 Twin and not the earler (and experimental) 4-input + EF86 model, which reportedly had so much treble that it didn't need a top-boost.
The TB unit has been claimed to have been designed as a measure to restore the brilliance found in the EF86-equipped amp but somewhat lacking in the AC30 Twin Normal.
So... when Hank describes the TB-in-the-back (which he does in that 1961 book), he is talking about a six-input AC30.
Elementary...
JN


