I once had one of those... complete with the gunslinger's holster rig and a box of .44 Center Fire cartridges. Mine was nickle plated... I went looking for a web based photograph and found this one... Damn, if I don't think it was the one I owned!!!! They are rare enough that it is certainly possible.
The one I had was not a "conversion" but a factory original... the Richards "Conversions" had their own serial numbers (mine was in the 1400s). Colt would convert guns from the field to the Richards-Mason format (.44 rim fire) on special order to their repair shop.