Maryland Code, Transportation § 13-104.1

(1) The manufacturer's certificate of origin for the vehicle, assigned by the transferor to the transferee; or

(2) If the vehicle was acquired in another state or country the laws of which do not provide for a manufacturer's certificate of origin, a certified bill of sale or other documents required by law in the other state or country, showing any security interest retained by the seller or created at the time of sale to secure the payment of the purchase price.