/1/ Stained (Environmental damage) /2/ Better titles - Opinion needed will get less view than "20xx shield cent with odd color and gunk on obverse" /3/ Stop watching YouTube videos - 99.44% of them are stupid or garbage or outright lies /4/ Welcome to CT
Oh, and /5/ Better photos. IN FOCUS. Crop to just the coin. Rotate to normal orientation (help us help you)
Probably just a yucky coffee cup holder coin with probably soda spilled on it. As a learning experiment, put it in acetone and see if it cleans it off.