Bud Jones double denomination errors are difficult to authenticate, but it is easy to do with Paulsons, C-Js, and others. You simply look at the cross hatching under high magnification. If the error is genuine, the cross hatching will blend into the inlay in perfect lines. On faked errors, the lines will be hopelessly mismatched. I have authenticated genuine errors and debunked phony ones for years using this method.