Revealing mistake: When Uncle Teddy sits down at the piano inside The Gold Nugget saloon, his finger/hand strokes don't match those of the music actually playing. In fact, a few times notes are struck when his fingers are not moving or even on the keys.
Other mistake: Snow Bird is noticeably missing from the Cheyenne prisoners during the lock-up, who would have probably interjected alongside Cloud Dancing to the soldiers.
Answer: A Cooper was someone who made various things out of wood including wooden caskets and even barrels.