Philip, I'm posting this to the list so you can't say I didn't do my homework. I tracked down a 4051 that I saw mentioned on the web and asked about it. Here's their response: Greetings Joe, I have had your e-mail on my to do list for sometime but the alligators have been chasing me on other chores. Any how The tek 4051 is about 1976 vintage and it is only recently that we disposed of them to our surplus place. We had 4051, 4052 ,plotter, joystick and a printer. I still have all the manuals and microfiche for them I think. The address for our surplus unit is <sniped>. I'm already working on trying to get the manuals and to find out about their surplus disposal. Joe