Parking meters installed in the parking lots shall be placed immediately adjacent to the individual parking spaces that shall be marked off and maintained in the lots. For each parking meter there shall be a clear indication, through use of a directional arrow, or an identification as to number with the parking space, to show which individual parking space it serves. Each parking meter shall indicate by a proper legend the parking rate and the maximum parking time, and, when the parking space is occupied and the parking meter put into operation by the insertion of one or more coins, the parking meter shall indicate on and by its dial and pointer the duration of legal parking, and, upon the expiration of that period, shall indicate illegal parking or over-parking.