Highway Use Permit (HUP)
December 1985, wide dies
Collection of the author

As I understand it, HUP plates were the precusor to apportioned plates in Vermont. Supposedly their use was discontinued in 1991. And yes, they really are blue!
December 1989, wide dies
Picture from Jim Moini - ALPCA #6215

Nice number.
December 1991, narrow dies
Collection of the author

At some point in the X series, the switch from wide to narrow dies was made.
December 1990, narrow dies
Private ALPCA collection

I think a few only of these exist with narrow dies, because this type was discontinued fairly soon after this style was introduced.
December 1990, narrow dies
Collection of the author

Not sure how far these plates made it - maybe no further than ABA?