In the golden era of the TV Western, Steve Mcqueen, the star of “Wanted: Dead or Alive” rode across black-and-white screens with a never-before-seen sidearm. His cut-down repeater, the Mare’s Leg, could be holstered like a revolver but fired with the speed and precision of a lever action rifle. This innovative weapon brought outlaws to justice every week – and rose to fame as the real star of the series.