The person producing an invoice for certification shall at the same time declare to the consul or vice consul the port in the United States at which it is intended to make entry of merchandise; whereupon the consul, or vice consul, shall indorse upon each of the triplicates a certificate, under his hand and official seal, stating that the invoice has been produced to him, with the date of such production, and the name of the person by whom the same was produced, and the port in the United States at which it shall be the declared intention to make entry of the merchandise therein mentioned.