The department and local authorities, with reference to traffic-control signs, signals, or markers owned by the department or local authority, are authorized to indicate the ownership of the signs, signals, or markers on the back of the devices in letters not less than 3/8 inch, or more than 3/4 inch in height, by use of a metal stamp, etching, or other permanent means. Except for employees of the department or local authorities, police officers, contractors, and their employees engaged in a highway construction contract or work on the highway approved by the department or local authority, it is a misdemeanor for any person to possess a sign, signal, or a marker so identified.
(ILCS Ch. 625, Act 5, § 11-313)