All numbers on business or residence houses in the City shall be of a figure not less than three inches (3") in height and approximately two (2) or more inches in width and shall be so placed as to be seen plainly from the street. They shall be purchased and paid for by the owner or agent of the property. The figures shall be of durable metal, glass or enamel, or they may be painted on neat design and durable material on the glass of the transom or the door. Perishable materials, as wood, paper and card, and marking of pen, pencil or other easily displaced substances shall not be deemed a compliance with this chapter. (Prior Code § 28)