As I understand it they were originated by the "Gunmakers" in order to weed put "Cheap" shotguns which were cutting into their market. They I think felt these cheap guns would fail proof & be removed from the market. In this they were only marginally successful I believe as many did pass proof. Further any gun which had successfully passed proof limited the maker's libility in case of a failure.
Having lived my entire life in a nation sans proof laws I will have to say the vast majority of "Questionable" guns as to safety & integrity, have been imported from nations which does have proof laws. I in no way feel handicapped because the US does NOT have them.
