Customs tariff amendment: changes tariff heading and raises ad valorem exemption rate for sponge iron under Customs Act powers. Amendment to a customs exemption notification substitutes heading No. 72.03 with heading No. 72.05 and replaces the previously stated ad valorem exemption rate with a higher ad valorem rate for sponge iron, made under the powers conferred by the Customs Act to amend exemption notifications in the public interest.