Section 1229. Sign required on privately-owned vehicle used in delivery of mail

1. Every person operating a privately-owned vehicle in  delivering
  the  United  States  mail  to  the addressee thereof shall affix to such
  vehicle a white sign, visible from the rear,  containing  the  following
  statement:
 
                                 U. S. MAIL
 
    Such  statement  shall  be  in black lettering at least four inches in
  height.
    2. Every person who violates the provisions of this section  shall  be
  punishable   by   a   fine  not  exceeding  twenty-five  dollars  or  by
  imprisonment for not more than  ten  days  or  by  both  such  fine  and
  imprisonment.