I found an old coin in my attic. I think it's Mexican or Hispanic?

The coin is a dark grayish color with white residue around a lot of the coin so I don't really want to clean it. The man is looking towards my right on the coin. Reading from right to left. "DEL.GRATIA.1776.CAROLUS.III." and on the other side it says... ".HISPAN.ET IND (1ND or IND).REX.M(M has an O over it, mint? =o).R.F.M." It's a little bigger than a U.S half dollar. On the back it has a coat of arms or something, a shield rectanglish, with a crown on top, and two pillars next to it with two ribbons coming from the back and wrapping around the pillars, on the left saying I think "I'L S" on the right "RA" On the shield there is a lion with a crown, sort of like a griffin on the bottom left and top right square, and a Castle or some kind of fort on the bottom left and top right. Then it has a couple of dents on the ridges and is not really even, hand-crafted most likely, and there are a couple of tic-like circles around the edges above and around the words. Also the ridges are - (Then a square like outline with only four dots for corners and a "-" inside.) - [ - ] - [ - ] - and so on. And that's about it except for the weird symbol on the back, on the shield on the bottom between the two.