I saw the didactic panels in the Huntarian museum in glasgow two weeks ago and they made an amusing note that numismatic experts across long time past had rejected the coins as obvious fakes, badly made, nobody could believe they were plausibly real being mould cast not stamped. Amateurish rubbish. The plos paper discusses scientific techniques which showed the provenance of the gold and its microstructure matching contemporary coins. They did look unbelievably crude.