Thanks for the information. I looked up the B&G on Utahrails.net. If the business car really was built for the Bingham & Garfield, it would have originally been narrow gauge and would have to have been built between 1874 and 1885. Since it was standard gauge, I think it may have been built for the Copper Belt Railroad or another of its standard-gauge incarnations, unless it was owned by the D&RGW or RGW. The name "Bingham & Garfield" was gone a few years prior to being standard gauged.
Info is scarce, so I am trying to figure out why the car is listed as being from the B&G.