The Silver Bandit (1950)

Tycoon Van Fleet Stooglehammer, owner of the Green Valley silver mine, sends his mild-mannered, milquetoast bookkeeper, Spade Cooley, out to investigate the robberies of his silver-wagons being pulled off by a masked-man, riding a golden palomino, known as the Silver Bandit. Spade, who can't ride or fight and can barely sing, still makes an impression on Molly Doren, sister of Frank Doren, superintendent of the mine, and makes an enemy of Sam Morrell, the mine manager. Spade suspects either Frank of Sam as being the Silver Bandit, but the sheriff, figuring nobody could be as inept as Spade, has his eye on Spade...especially after he nabs Spade riding...uh...trying to ride the bandit's horse and wearing his costume.