Pandora's Luck — Gilbert M. Stack

From the pages of Alfred Hitchcock's Mystery Magazine: Miss Pandora Parson is a lady gambler making her living in the rough and tumble West of 1874. William Steed is a manager willing to run over anyone to establish the reputation of his new prize fighter. Corey Callaghan is the young bare-knuckle boxer who stands in his way. When the three meet up in Denver, there’ll be crime to pay.