It's literally dirt. Worth face. You could probably clean it off. Kind of weird though. By the way, welcome to CT.
Welcome to Coin Talk! My advice to you (if you already haven't) is to start reading some numismatic literature about how the minting process works. Red book is a good reference for a beginner and there are a lot of sites to help you with the process. There is a "thing" of looking to much for something. Sometimes you see something that just isn't there. Keep sharing with us! Thanks!