Re: A Bad Day For PRR Boxcar 566640
The Temple Library web viewer has a neat function allowing you to rotate the photo by 90 degrees - handy to view this upside-down car! I don't see markings for ballast - perhaps you are seeing the "BALTIMORE AND OHIO" which would be at the top left of the car. I also see the KY 12 48 indicating its inspection at Keyser, WV shops in Dec 1948. (I believe)
I'd say this is definitely some variant of a covered hopper given the markings, the number (630121) and the unloading apparatus on the bottom. (the four square chutes.) The rivets for the slope sheet is visible on the left. What I don't see, and what is puzzling to me (given my lack of reference material) is that there is no visible riveting for the inner, center slope sheet. The "upside-down V" normally seen on the sides of covered hoppers. Instead there are four rows of rivets along the bottom.
There's definitely a visible squared off roof line/top edge, so it's not a wagon top, although the wagon top covered hoppers had very similar numbers. See some of the N-34 prototype photos on Spring Mills Depot's page: http://www.springmillsdepot.com/n-34prototypephotos.htm
N-31 630200 builders photo for reference http://rr-fallenflags.org/bo/bo630200ago.jpg
Unk class 630874 http://rr-fallenflags.org/bo/bo630874ago.jpg
I dunno. Perhaps someone with the B&O freight car diagrams can home in on the class. Too bad the retoucher took so much liberty. :)