Section 157, The Customs Regu- Citation

In addition to or in lieu of documentary permits the !?ent~aofficer responsible for the issue of such permits may issue or cause Ion a ges. to be issued, at the expense of an applicant, permits which may be in the form of metal discs or other means of identification authorising the persons to whom they are issued to enter a Customs area or any specified. part thereof during the time for which they are issued.