The license plates required on every motor vehicle by the laws of the State, or by the laws of any other state while such vehicle is operated within the corporate limits of the City, shall be kept clean at all times and clear, distinct and free from grease, dust or other blurring matter so that they are plainly visible at all times.during daylight and under artificial light at night, and shall be attached in such a manner as to be clearly readable at a distance of 100 feet, and under no circumstances shall they be obstructed by any portion of the vehicle.
(1958 Code § 16.111)