Ohio Rev. Code § 4549.10: Operating manufacturer vehicle without placard.

(A) No person shall operate or cause to be operated upon a public road or highway a motor vehicle of a manufacturer or dealer unless the vehicle carries and displays a placard, except as provided in section 4503.21 of the Revised Code, issued by the director of public safety that displays the registration number of its manufacturer or dealer.

(B) Whoever violates division (A) of this section is guilty of illegal operation of a manufacturer's or dealer's motor vehicle, a minor misdemeanor.