These plates were used by enforcement agents for the Motor Vehicle Department. This function is still in existence today, but it has been a long time since they last used special plates. Their vehicles now use the standard-issue “State” plates with a ‘1’ department code prefix.
I don’t know much else about this type yet, I’ll update this page as I research more.
I believe this may actually be from Rhode Island, but I received it with the plate to the left.