It shall be unlawful for any person to display on or near the premises of any place of business in this state any advertising medium which advertises the price of motor oil offered for sale without conspicuously showing on the same advertising medium the brand of the motor oil and the name of the product. The letters, figures and numerals used to designate the brand and the name of the product shall not be less than one-half the size of the numerals designating the price.