What does the arrow mark on defence vehicle number plates mean?

Unlike other license numbering systems, defence vehicles have a unique numbering system. The numbers are registered by the ministry of defence in New Delhi. The first (or the third) character is always an arrow pointing upwards. The next two digits (or the two preceding the arrow) signify the year in which the defence department procured the vehicle. The next is the base code, followed by the serial number. The letter ending after the serial number indicates the class of the vehicle. The arrow prevents the number from being read wrongly in case the number plate (and/or the vehicle bearing it) turns upside down.