I have a Proton 450 Tuner, a Proton 550 Integrated Amplifier, and an NAD 5420 CD Player that I bought in the early 80's. All working and in excellent condition.
I had boxed them up because of a number of successive moves, and just recently started setting them up to use in my office. Unfortunately I can't find the user manuals [I have the service manuals] for each.
I am posting this notice on every audio or stereophile group I can find on the Internet. If you have or know of anyone who may have these and are willing to make copies [I will pay all expenses] please contact me!