Your find got me digging a little. I searched Railway Age v 66 and v 67  [I found there on-line at archive.org] for this order and found it in Railway Age v 67 p. 182.
The Champion Fibre Company, Canton N. C, has ordered
one 50-ton steel hopper car from the American Car & Foundry
I am not sure what to term the hopper car in this order, but AC&F was building USRA 55-ton hoppers at the time so it apparently filled this order with a similar if not a car identical to the USRA design. Note the order was for a 50-ton hopper, but ACF built a 55-ton one for CFCX. I am not sure if the lot number would be of help such as referencing another order so this single hopper actually was an add-on to that other order.