The Clad layers are composed of CuproNickel. That's Copper mixed with Nickel. It can tone that color a few other ways.
If you have been following CT since you joined in 2017, you may have seen several posts from @paddyman98 of the coins he has found while metal detecting. He shows many, many coins with environmental damage, that changes the entire look of the coin, but does little to increase the value.
My coin had a shine to it that made me think it was not in the ground. I have not metal detected for several years now, need to get back into it. I do expect it to become a very popular thing by the end of this decade, might not be as fun with all the crowds during then.
By the end of this decade? Metal Detecting is very popular at the moment! There are many YouTube channels and Instagram pages dedicated to detecting. Clubs and events are held all over the country all the time. My Instagram page has almost 2000 followers who are mostly into Metal Detecting Check it out at.. bunnyfoofoo_dirtydigginnuts I'm going from NYC to Rock Hill South Carolina next weekend for the following event with 150 attendees!