Section 236 - Prima facie proof1. In any action relating to the enforcement of any provision of this article, a certificate duly issued by an assay office of the treasury department of the United States, certifying the weight of any article, or any part thereof, or of the kind, weight, quality, fineness or quantity of any ingredient thereof, shall be receivable in evidence as constituting prima facie proof of the matter or matters so certified.2. In any action relating to the enforcement of any provision of this article, proof that an article has been marked in violation of the provisions of this article shall be deemed to be prima facie proof that such article was manufactured after this article became effective.