What's up with this? I feel I see this all the time, except more frequently in the US. I saw one yesterday on the back of a Beemer with "DK" in an oval, and from memory I can recall "PL"'s in ovals. There's many more combinations I've seen, too. They're always bumper stickers (or magnets, who knows) and they're always placed on the trunk, and never the bumper.
What's up with it? Is it a gang sign?
Edit: Never mind. I answered my own question by doing a bit of searching. Apparently it just shows what country you came from.
http://www.stickercafe.com/ovalstickerhistory.htm
So I guess I saw a guy from Denmark in a BMW yesterday then. That's not very gangster at all.