The original design was, literally, scribbled on a piece of scrap paper. It was a Tim design that he wrote down to explain how an amp worked. John paid something like £20 to Tim for the piece of paper. It was a good design which Tim refined for John Shearne but was never really a proper, bespoke design.
I seem to remember Tim designed the amps for him which is a huge plus...
I also remember that Steen used to design some very nice speakers too.
Tim took the 'design' to Zia Faruqui to make for him.
Steen Doessing made some excellent and interesting speakers including his 'ribbons' which he made from Bacofoil.