Not an error. The Numeral 6 took a hit, probably from a coin counting or coin rolling machine.. very common occurrence
There is no damage to the field around the 6. Any mechanical damage after minting would undoubtedly show disruption of the field. Simply calling it a ding dodges the real answer. Could this have happened when a second strike was made?
You have asked a good and challenging question. I will explain what I know. First, there is no known error to attribute to the OP's Cent. Second, Coin Roll crimping machine damage involves the last digit of the year. There are many examples of this kind of damage from the 40's, 50's, 60's and 70's.. because of the time they were minted any damage would of been worn away due to circulation over the years. There have been plenty of posts on CoinTalk with the same question. The conclusion has always been PMD - Post Mint Damage due to Coin Wrapper Machine damage. There is no double strike. Here is another example -