When a property identification number has been designated by the City Engineer, the owner or occupant of such house or building shall cause a painted, carved or cast duplicate of such number at least three inches (3") in height and varying in size according to the setback distance of the structure and of a shade contrasting with the background upon which the number is mounted to be located on the structure as provided in this chapter. Such number shall be block numerals (not script) and shall be located in a conspicuous position upon the portion of such structure which faces the thoroughfare identified in the address certificate. The property identification number shall be mounted in a permanent, stationary and durable manner, unobstructed at all times by vines, screens, or anything that would tend to hide or obscure the number, and at a sufficient height that the number will be clearly perceptible with the unaided eye from the centerline of the thoroughfare upon which the structure is located. (Ord. 17-30)