The gun is most likely a Great Western
Great Westerns were offered in the standard barrel lengths of 4.75", 5.5" and 7.5" and mostly in calibers .45 Colt, .38 Special, .357 Magnum, .44 Special and .22 Long Rifle. They looked so much like Colts that an original Colt was used in the early advertising. There are subtle differences in the shape of the trigger guard and overall grip frame, while the front of the hammer, when cocked, looks like an upside-down "L" since the firing pin is mounted in the frame. Great Westerns were very popular in both movies and TV shows, and used extensively by fast draw artists of the time.
It is well know the Arness "GunSmoke" revolver was a Great Western and Sternbridge had hundreds of them, as did Hollywood Costumes both Hollywood Rental gun lockers