Back when electric vehicles were still a novelty, the State used a small number of them in its vehicle fleet. Information on these plates is hard to come by but these plates have the 5- prefix indicating they were used in the general motorpool, and an EV designation in the serial.
In the 1970s there was also another series of these plates, in a 1TEST1 format, in the standard white/blue style.
1990s
The 5- prefix indicates it was issued to a vehicle used in the general motorpool.