Jason,
I think there may have been only one of these. I know it was used on the Silverton Branch, and had been fitted to #463, and maybe 464. There is a picture whick shows engine 476 parked behind the plow so close it appeared to have been installed on that engine, but it seems to be an illusion peculiar to that photograph only. Fooled me, though.
I seem to recall Jerry Day had some comments on this paticular plow at one time, maybe he can fill us in again. This plow was at one time installed ( and perhaps even built for use) on a modified high side gon, I believe. There are drawings somewhere.
Mike