Apropos. "Type-X" machines, I seem to remember (vaguely!!) that when I went through the Ground Wireless Fitter's course at RAF Compton Bassett in about 1956, we were still taught about said machines and shown and "worked" on how to service them. Please do not ask if I have any notes because, although we did take notes they were taken from us before leaving the "secure" classroom and destroyed!! Happy days!
Bill