What a good way to find errors on coins is to go to a vending machine, put in a quarter and press return change so you get a new quarter (or whatever coin you put in). My friend has found a wisconsin state quarter with an extra leaf. The machines usually have many coins that you can search through.
Lol - I've done this before at hotels at night when I was bored - grabbed some coins and started rotating through them. I've never really found anything really good, but I did find a 1942 war nickel and some misc coins for Whitman books when I was a younger
