There shall be a uniform system of numbering all houses, stores, and other buildings (except sheds and outbuildings), erected or to be erected within the city limits, by placing on the door or doorframe of the main entrance to said buildings, or as near thereto as practicable, the number assigned thereto as hereinafter provided; said numbers to be painted on the building, or on glass or noncorrosive metal, or a noncorrosive metallic figure used, at the option of the owner, so placed as to be readily seen from the street. The figures designating the number, whether painted or otherwise, shall be not less than three inches in height. (Ord. 369 § 1, 1917)