Look for such errors on new coins (uncirculated). You can't easily find them on well circulated specimens. Even so, they are not wroth a lot. You ought to go to a coin show.
The 1st photo is one I found on Pinterest that shows part of the error. Obverse side of 1776-1976 no mint quarter looks like the 1976 could be DD. On Reverse on the last S on Pluribus starts a crack that continues to top of arm then stops. It begins again at bottom of arm to top of the drum. Another crack starts at the bottom of drum between the E & R and continues to the rim of coin. At the top of the coin above STATES there are 2 small “at the top of rim,also in STATES the last S


