I collect wheat pennies, the pennies in the US that were made from 1909 through the late 1950's. They are still in circulation, but kind of rare. Last summer I got a 1907 Indian Head penny in change. I looked at it for a very long time, thinking about all the places this penny has been in the last 113 years, going from pocket to pocket, cash register to cash register. And all this time, no one noticed what a rare coin they had.