If the mintmark actually touches one of the numbers in the date it then does become more valuable. There are many mintmark errors including doubling and tripling, a sideways mintmark with the correct placement punched over it, and so many others that are very cool. I got a penny in change where the copper coating was never applied over the zinc so it was silver colored. I got it authenticated for $8 and sold it for $75 at the time. Keep looking close, you never know when a valuable error will come your way...Ryan