Chewin' gum! Oh. @LaCointessa beat me to it. Just kidding. I agree with @paddyman98 that it looks like old solder.
The key point is none of this type of stuff matters to 99.999% of numismatists, honest it doesn't. The ONLY exception would be a guy assembling a display of abused coins.
I am new to looking at coins. If I ever see something similar again, I will think "solder" - which, for some reason, did not pop into my mind. I am happy to know what it is and my curiosity is satisfied. I understand why 99.99% of collectors would not keep such a coin, but, @The Bob, as students, I agree we should have a natural interest to identify unusual metal cud-like structures we find on our coins before deciding to exclude them.