§ 6814. Records of shipment. For the purpose of enforcing provisions of this article, carriers engaged in commerce, and persons receiving drugs, devices or cosmetics in commerce or holding such articles so received, shall, upon the request of an officer duly assigned by the secretary, permit such officer, at reasonable times, to have access to and to copy all records showing the movement in commerce of any drug, device or cosmetic, or the holding thereof during or after such movement, and the quantity, shipper, and consignee thereof: and it shall be unlawful for any such carrier or person to fail to permit such access to and copying of any such record so requested when such request is accompanied by a statement in writing specifying the nature or kind of drug, device or cosmetic to which such request relates: Provided, that evidence obtained under this section shall not be used in a criminal prosecution of the person from whom obtained: Provided further, that carriers shall not be subject to the other provisions of this article by reason of their receipt, carriage, holding or delivery of drugs, devices or cosmetics in the usual course of business as carriers.