Auctioneer signs may hereafter be erected as follows:
(a) Such a sign, which may be lettered on both sides, shall not exceed, in the aggregate, twenty-four square feet in area or display surface, counting both sides, and shall not exceed six feet in height above the ground level.
(b) Such a sign shall be set back at least twelve feet from all property lines when possible, or half the distance between the sidewalk and the building when the property is closer than twenty feet from the sidewalk. No such sign shall be placed on a street, sidewalk, boulevard or public right of way.
(c) Such a sign shall be removed within forty-eight hours following the close of the auction.