Every person who uses a postage meter that is owned, operated or has been installed by any state department, board, commission or state educational institution, for his own personal use, or to the use of any person not entitled thereto, without authority of law, is guilty of a misdemeanor. Each state department, board, commission or state educational institution which has installed a postage meter machine shall place an imprint plate on such machine showing: first, that the mail carried by such postage is official State of Oklahoma mail; and second, that there is a penalty for the unlawful use of such postage meters for private purposes. The installation and cost of such imprint plates shall be paid from appropriations for postage and contingent expenses made to the various state departments, boards, commissions or state educational institutions.