One freestanding sign advertising the name of the station or garage and the principal products sold on the premises, including any special company or brand name, insignia or emblem, provided that each such sign shall not exceed 35 feet in area on a side and shall be set back 20 feet from street lines and 50 feet from side lot lines and provided further that the sign shall not be less than 10, nor more than 20, feet above the ground.