Nice find! At first I thought it might be a dandy button but maybe look into the counterstamped/countermarked Reis coins of Portugal /Brazil. That could be a Portugal arms counterstamp in the center. And your location on the MD shore would not be out of line for finding something like this.
If I don’t zoom in it appears to be a wiped US Large Cent. Sort of see a bust in the first photo, sort of see a wreath in the second. Maybe Matron Head.
The stars seem to be closer to center than us large cent and matron head. It is slightly concav which makes me think could be button. Very thick and heavy though.
I’d say button, just because there is what looks like a spot where a shank may have once been and the stars around that look like a makers mark, very cool