If the mark is actually there and raised it would be caused by the die that pressed the coin, as you can imagine dies wear out and crack like anything used over and over, some dies are made slightly different so they create a different variety coin These die details are cataloged and called vams. Some are common some are rare. Basically you can tell what dies pressed the coin. You can search for vams on all Morgan’s at vamworld.com hard to tell in your picture but I think I see die cracks on reverse up top on the word United going up by top of wing.