Unrelated
But in the US state of Missouri, the governor's office can issue special plates consisting of only numbers (up to 4)
Supposedly it is done as a status symbol, though the real reason is it serves as a way of letting the cops know you are an Important Person and shouldn't be bothered with petty stuff like driving 20 mph over the speed limit or parking in a no parking zone. Especially the two digit plates, apparently you can get away with almost anything driving around in one of those.
There may be something similar in other states, I don't know, I just recall this because I had a resident explain this to me when we saw a big SUV parked right next to a fire hydrant in front of a bar. It had a two digit plate, and she knew that it was Augie Busch's car (heir to the Anheuser Busch fortune) since everyone in town knew it was his by the two digits.