A copy of the application for a license to conduct a sale under this Ordinance, including the inventory filed therewith, shall be posted in a conspicuous place in the sales room or place where the inventoried goods are to be sold, so that the public may be informed of the facts relating to the goods before purchasing same; provided, however, that such copy not show the purchase price of the goods. The duplicate copy of a license issued hereunder shall be attached to the front door of the premises where the sale is conducted in such a manner that it be clearly visible from the street. Any advertisement or announcement published in connection with the sale shall conspicuously show on its face the number of the license and the date of its expiration.