Not to pile on with regard to "accuracy" but I noted the aluminum horse shoes on all the horses as they charged forward just before the Battle of Grapevine scene (about 2/3rds the way though part three). I'm not sure when aluminum horse shoes became widely used but I know it wasn't in the 1880's.
I totally missed that.
As for when aluminum was used first, not a clue.
My father (also a farrier) taught me aluminum, steel, iron and magnesium. My Grandfather taught him so your going back to the 40s.
My wife informed me that aluminum shoes are common in the U.K., especially in racing circles.