This is a Buda Model R-1 Multi-Gauge Gang Car. They were developed for the Army. I don't know how many of these the Army purchased overall, but four of them ended up on the WP&YR in 1943. Two were wrecked in 1944 and the remaining two were shipped out in 1945. Buda filed for a patent on this design in 1943, but the patent did not issue until 1947, after there was no more market for this car. Buda probably spent a lot of time & money arguing with the Patent Office over the scope of the patent. The lawyer probably made good money on this argument - Buda, not so much.
Buda R-1 (a).pdf
Buda R-1 (b).pdf
Buda R-1 (c).pdf
Fairmont also made some multi-gauge gang cars that they designed for & sold to the Army. Again, I don't know how many overall, but five ended up on the White Pass in 1943. The last of these five Fairmonts lasted until 1976.
Robert