Sounds like a mid-70'd Black Beauty with a Super Sensitive throwoff -just guessing blindly, though. Without being able to see a picture of it, it could be just about anything these days.
My feeling is that if it's only thirty years old, then it shouldn't be that beat up if it had been in the ownership of someone who cared about it. Since you say that it is, in fact, beaten up badly, then it's probably not worth that much....but I'm not going to venture a guess about it's value without seeing first. Pictures are crucial -the more detailed, the better.