The Office of Regulatory Staff, upon the presentation of a certificate from the Office of Regulatory Staff authorizing the motor vehicle carrier to operate and upon payment of the proper license, must furnish the motor vehicle carrier with a distinguishing plate or marker, which, in addition to the other matters otherwise provided by law to be placed thereon, shall bear the letter stating the class under which the motor vehicle shall operate, such as A, B, C, D, E, or F.