In the case of articles of merchandise made in whole or in part of gold or of any of its alloys so imported into or exported from the United States, or so deposited in the United States mails for transmission, or so delivered for transportation to any common carrier, or so transported or caused to be transported as specified in section 294 of this title, the actual fineness of such gold or alloy shall not be less by more than three one-thousandth parts than the fineness indicated by the mark stamped, branded, engraved, or printed upon any part of such article, or upon any tag, card, or label attached thereto, or upon any box, package, cover, or wrapper in which such article is incased or inclosed: Provided, That in any test for the ascertainment of the fineness of any article mentioned in this section, according to the foregoing standards, the part of the article taken for the test, analysis, or assay shall be such part or portion as does not contain or have attached thereto any solder or alloy of inferior fineness used for brazing or uniting the parts of said article: Provided further, That, in addition to the foregoing tests and standards, the actual fineness of the entire quantity of gold or of its alloys contained in an article mentioned in this section, including all solder and alloy of inferior fineness used for brazing or uniting the parts of such article (all such gold, alloys, and solder being assayed as one piece), shall not be less by more than three one-thousandth parts, in the case of a watchcase or flatware, or than seven one-thousandth parts, in the case of any other such article, than the fineness indicated by the mark stamped, branded, engraved, or imprinted upon such article, or upon any tag, card, or label attached thereto, or upon any box, package, cover, or wrapper in which such article is incased or inclosed, it being intended that the standards of fineness and the tests or methods for ascertaining the same provided in this section for articles mentioned therein shall be concurrent and not alternative.