... in order to ensure uniform application of the nomenclature of the Common Customs Tariff, provision must be made for the classification of the following types of pig fat: (a) obtained by the rendering of pig carcases from which most of the meat, edible offals and fat have been removed ('choice white American hog grease'); and (b) obtained by the mixing of lard, the product described at (a) and rendered pork fat ('rendered pig fat') ...