On the headstock (motor) should be information indicating the year it was manufactured. I bought a 1996 model ( Mark V 520) for $650. It had no rust, a bandsaw, joiner, all tools for Tablesaw, turning tools, castors, table saw blades, extended table for table saw, removable safety on/off switch, and a ton of other woodworking assessories (non shopsmith related). I didn't get any manuals.
If you google "buying a used shopsmith" you will get information on what to look for when buying a used shopsmith. I highly recommend using it, wished I had known about the information before purchased, although I would have still purchased my SS.
It has been a great tool for me. I've made many pens on it and venturing into larger projects.