Bruce, looking at your photo
http://wpyphotos.com/passenger/excursion-flats/ExcursionCoachFlat-386565.jpg
do you know what the lettering is at the end of the car? Something ...R&N Co.?
I spotted similar notation on one of the old cars at Coal Creek but have yet to figure it out.
See photos IMG_0309, IMG_0310 and IMG_0311 linked below. Sorry, I didn't know how to link directly.
http://www.flickr.com/photos/610bs/albums/72157676831881743
IMG_0312 and IMG_0313 shows car 511.
I heard WP&YR cars 511 and 521 or 522 were sold to the Coal Creek operation in 1909.
I found a bunch of old red boards near the power plant at Coal Creek which I thought looked like pieces of a box car however, based on the location of lettering on car 511, it couldn't have been a box car when it arrived at Coal Creek. Perhaps one of the other remaining cars was a box car.
Dave