When such application is filed, the city clerk shall register such taxi or vehicle in a book to be kept by him for such purpose, and shall issue to the owner thereof a certificate showing such registration and the purpose for which such taxi or vehicle is offered to the public for hire. Such certificate shall be at all times carried in the taxi or vehicle and displayed in a place visible by passengers of such vehicle. Such certificate may be transferred from one vehicle to another by the owner to whom the certificate was granted upon giving notice to the city clerk of such transfer, and by registering the serial number of the motor and description of the vehicle to which the certificate is transferred. (2000 Code § 16-204)