$800 for a good condition Hamiltonian Set is a great deal. I've seen them go for $2k with a box. I have an original that isn't as nice I paid about 700 bucks for. I have an MTH flavor of the cars and they are really nice. I think the MTH offering may have depressed the prices a bit. I'd still keep my originals.
I don't remember however I do think they were made by AC Gilbert in New Haven, CT (not in Chicago). I like the stuff that was made here...