Current normal series (1966/74 - ), IB (2nd and 3rd letter) = Armagh, example of an illegal spacing (correct spacing is NIB 1242)

Former normal series (1958 - 1965/74), MZ = Belfast County Borough, front plate (black on white since 1968)

Former normal series (1958 - 1965/74), FZ = Belfast County Borough, silver or white on black prior to February 1968, original 1962 registration