Okay. I did my search and came up with a gazillion pages on the subject and I'm dizzy! So here's the question. What are the defining traits of a 4001 compared to the other Ricks? (i.e. 4003's etc...) I'm pretty sure mine's one, but not positive. (Feb. 1976 build date.) Please help and then I'll get rid of the thread so it doesn't cause any concern that it's too repetitive a subject.