(a) All motor vehicles and trailers shall be adequately identified as property of the office by the affixing of suitable seals or by other methods showing suitable insignia or description.

(b) The county superintendent shall designate the normal storage location for all motor vehicles and trailers under his jurisdiction, and all such vehicles and trailers shall normally be garaged at such locations.

(c) Motor vehicles and trailers shall be used only in the conduct of official business; i.e., driven, or in the case of a trailer drawn by a motor vehicle driven, by the county superintendent or by an employee of his office acting in the performance of, or necessary to, or in the course of, official duties. Any other use, including use for driving to and from the county superintendent's or the employee's home, unless the county superintendent or the employee is departing or returning from an official trip or unless his home is the officially designated storage station, will be considered misappropriation for private use.