The pan would have had a maker's mark of some type. (The pan is the round part of steel.) The maker's mark has probably gotten too rusty to read. It might be a Blake and Lamb trap; most of these had an stamped imprint on the pan, where many of the Victor brand traps had a 'V' cut out in the pan.
Personally, I don't think the trap is all that old. Lots of people still run trap lines, even though fur prices are very, very low.
FWIW, traps are still manufactured and sold. They can be a hot commodity on ebay, but generally if you have lots of traps in a lot, like six or more. If you were selling it, you might get $5 for it.