§ 236. Prima facie proof. 1. 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.