I researched all of the files at the CRRM when working on the two volume D&RGW/RGS snow fighting book project. D&RGW records just were are not that detailed. I doubt if there is any D&RGW guy from era still alive, but hope I am wrong.
It is interesting that OM might have been scrapped. The plan was to bring Rotary OO from Gunnison to Alamosa in 1955. It was newer, more efficient, and same blade design as OY. The Trainmaster was supposed to bring it to Salida at the rear of a train of stock cars, but he was afraid to do it according to Bob Richardson. He kept leaving it behind each time they ran a train and when D&RGW management in Denver learned, it was too late. They did not want to do a special train for it, so it was left in Gunnison and sold to a local guy. It was scrapped, the boiler used to heat the roundhouse which was being used as a county garage. The tender ended up on a ranch out on the Baldwin branch and I found it in 1974 and took over 100 photos of it.