(a) All packages containing any goods, wares, or merchandise
manufactured, produced, or mined wholly or in part by convicts or
prisoners, except convicts or prisoners on parole or probation, or
in any penal or reformatory institution, when shipped or
transported in interstate or foreign commerce shall be plainly and
clearly marked, so that the name and address of the shipper, the
name and address of the consignee, the nature of the contents, and
the name and location of the penal or reformatory institution where
produced wholly or in part may be readily ascertained on an
inspection of the outside of such package.
  (b) Whoever violates this section shall be fined under this
title, and any goods, wares, or merchandise transported in
violation of this section or section 1761 of this title shall be
forfeited to the United States, and may be seized and condemned by
like proceedings as those provided by law for the seizure and
forfeiture of property imported into the United States contrary to
law.