These cars date back to the early days of N scale (late 60s / early 70s). Bachmann also sold them under their "Parkway Industries" label (same model, same clamshell box, different brand name). As of this 2016 writing these models are only available as part of Bachmann trainsets (IE not sold separately).
I don't know what specific prototype this model might be based on (if any), but it bares at least a passing resemblance to the composite gondolas designed by the USRA during World War I.