It is a version/facsimile of the Conversion Buffalo Bill owned, a 51 Navy , I believe BB's was cut to 5 5/8 " bored through Cylinders
chambered 38 long.
I have similar gun & holster though my project was on a 7 1/2 " Richard & Mason cut 5 1/2 " tuned by Long hunter
it chambers 38 Spcl. the holster was made by a good friend.