coins are more common than you think and some (most ) are very affordable . I have maybe 100 that are double stamped or all of the image not on the blank . I use to buy bags of pennies , nickles and dimes just to look for error coins . I have been lucky to find a few here and there ( back in 1992 a bag I bought had over 100 double struck pennies ) I made a nice killing on them . I am also the proud owner of a 1955 REAL double die i was able to get for 1500.00 many many years ago . however chip errors are still 1000x more rare than any coin errors and I have yet to find even one with 20 years of collecting !