Here is something else to ponder... occasionally, very occasionally new examples are found, and you don't have to be a seasoned vet to make a new discovery. If you believe you have a doubled die and cannot find it on one of the three sites referred to in this thread, present it here to us in Modern Errors and we'll take a look for you. We have had members here make new discoveries all the time, so maybe you found one that has been discovered but just not listed yet, or it could be a whole new discovery! Just remember that not all coins are error coins, and error coins are rare. But someone has to make discoveries if they happen, and it just could be YOU! Happy hunting!
