Where can you find information about a 1975 Lincoln penny with the state of Illinois stamped on it?

AnswerThis is a novelty coin -- one of fifty states that were stamped onto normal pennies by a private company to make up sets with all the states on them. They were usually mounted on some kind of board and sold for a few dollars.

I saw a set sell on eBay recently for about $20, but the individual coins have little value.