In New Jersey, any plate issued since 1959 is still potentially valid, and can be used on the road if it has been continuously registered to a vehicle since it was first issued.
If a plate is no longer registered, it cannot be re-issued as a regular passenger plate, but apparently old number combinations can be requested as vanity plates - if they are old enough and are not currently in use.
Replacement remakes have the same pattern as the original plate (with the separator).
Vanity remakes have no separator (usually a space where the separator should be).
And ... here in New Jersey, ... with every rule, of course there is an exception. Or two.
This plate is too new to be a vanity remake (the number is from 2001) but it has been remade as a vanity - it fits the pattern for vanity remakes.
It was on a 1993 Z28 (thus the value of the "93Z" part of the serial).
JJ233Z is also too new to be a vanity remake (originally from 1995).
ABC123 and SUE101 are old enough, but on both plates, there is no space where the separator should be.
Errors, or on purpose ? Who knows...