Frank,
My Dad was an engineer, and he had a set of those tools that he gave to me when I was in High School when I had aspirations of becoming an architect. The brand that we had was Keuffel & Esser (I think that's the correct spelling /forums/images/graemlins/crazy.gif). K&E were supposed to be some of the better quality drafting tools around. But I couldn't really tell you what their worth might be.
Why don't give you give a call or stop by your local Technical College and talk with one of the drafting teachers? They'd probably have similar sets that you could compare yours to, and maybe even have an idea of their worth. /forums/images/graemlins/smile.gif