O Scale Models:
Chooch #674 Pullman Flat Car – Ultra Scale line of resin cars.
Wiseman Model Services appears to be producing a similar kit.

The History:
The American Association of Railroads (AAR) Committee on Car Construction established a standard for 53’ 6” flat cars based upon a 1941 Pullman-Standard Company design. The earliest users of this design were the Chicago Great Western, Monon, Soo and UP. The design established a new standard for deck height of 42” which was lower than previous car designs. This feature would permit taller loads without exceeding established clearance limits. It also had a much wider deck extending beyond the fishbelly sides. Twenty railroads built 2532 cars to this basic design.

The car spanned a long period of operation ranging from 1941 to the 1980’s. Some roads converted these cars into piggyback carriers or fitted them with bulkheads for building materials. Many of the cars ended up in maintenance of way service after a long revenue life.

Following chart from Chooch website: