Ahhh, folks, notice the OP stated this one he's inquiring about is 1) a blued Bisley and 2) a .41 magnum and has a 5 1/2" or 6" barrel! Then all that was asked is if was an unusual model. So...
For starters there's not been a blued Bisley in .41 magnum made available from Ruger. Secondly, the .41 magnum has not been available in a 5 1/2" barrel configuration other than the stainless Bisleys produced for Acusport and then later, Williams'. Couple those two together and it's pretty certain this is simply something someone had done, or did it themselves. Pretty easy to do. Gonna take a guess that it was either a Bisley someone cut the barrel down on. (can tell from the barrel rollmarks) or a standard BH that someone cut down and Bisley-ized.
Regardless, great chambering in a great configuration.