They are common, It happens when the die striking the coin has debris "Grease" stuck to it. This prevents all of the elements of the coin from striking. Most of the time it is a small section of the coin like a few letters. I think your coin is neat but still not worth a lot if that is what you are asking.
You can call it the Hannibal Lecter quarter since his mouth is covered so he can't bite. Sell it on ebay for $100,000. lol