Good one! I like that.
Sorry to be so, uh, proprietary in the conversation. In Montana (and WY and maybe some other states) our license plates have two sets of numbers separated by a hyphen. The first number designates what county you are from (1 - 56) and the rest is just random. SO...Missoula for example, is known across the state as the liberal, tree-hugging, hippie town tucked inside of western Montana. The rep is earned, but misguided.
Anyway, a license plate that starts with a 4 is from Missoula Co and everywhere you go the rest of the "locals" have an opinion of you before you step out of you rig. One of my favorite bumperstickers ever states: I love Missoula, great little town and only 30 minutes from Montana!
Anything in the 50s means you've ventured in off the plains (or out of the deep NW) and are lost in the "big city". A 1 states proudly that you live in Butte! And so on...