The Fighting Sheriff(1925)

As a result of a blow on his head, suffered when he was robbed of a shipment of platinum by a gang of bandits known as the Wolf Pack, Sheriff Larry O'Donnell loses his memory and disappears for several months. Jeff Baines, leader of the outlaw gang, uses Larry's absence to get himself elected sheriff. Larry regains his memory, secures proof of Baines' guilt as the leader of the Wolf Pack, seals the evidence into an envelope, and gives it to Madge Blake, the postmistress, to mail to the governor. Baines and his henchmen attempt to rob the mail coach to stop the latter but are captured in a trap set by Larry.