That would probably be a hard one to pin down, that particular Ranch Craft lamp was made using components of the Dietz Comet lantern, they made other western themed electric lamps also. I'd guess they are mid 60s'to 70's, the trademark, Ranch Craft Originals, and the RC trademark were filed in October of 1965 and was owned by Dunning Industries Inc. in Greensboro, NC. The Trademark expired in October, 1987. That probably won't help much to get an exact date but it might help.
W.M.