Any person who violates any provision of this subtitle, and each of his managers, managing agents, directors, or officers who directly participates in a violation or consents to a violation, is guilty of a misdemeanor and on conviction is subject to a fine not exceeding $500 or imprisonment not exceeding three months or both. It is a defense to any prosecution brought under this subtitle that the item concerning which the prosecution is brought was manufactured before July 1, 1912.