AlanMcKillop wrote:What was the difference between Stadium and Truevoice (which was what I thought Hank used)?

RSA/Truvoice was the British amplifier brand which Selmer had acquired in the 1940s and on which they eventually changed the name. The amps - or at least, some of them - were at one time marketed as Selmer-Truvoice units, but known by model names including Auditorium or Stadium. The name "Truvoice" disappeared off the amplifier range at about the time that the famous croco-skin models were introduced (maybe just a little later than that) but remained on certain accessories (like their rubber contact mike for acoustic instruments).
In effect, it was a bit like "Vox" / "Jennings". Not exactly the same, but Selmer and Truvoice were company names whereas the bit after that was the model.
There's a really good history of Selmer (amplifiers) on the web at:
http://www.vintagehofner.co.uk/gallery/gallery3/stor.htmlI've helped them out with a couple of sixties catalogue illustrations in the past.
JN