Parking meters installed in the parking lots shall be placed adjacent to the individual parking spaces that are to be marked off and maintained on the lots. For each parking meter there shall be a clear indication, through use of directional arrows or an identification as to number within 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 applicable to vehicles parked at that meter 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 overparking.