These models are available with either a horizontal brakewheel or a vertical one.
They are also available with "one and a half" doors (and with the aforementioned brakewheel variants) -
In addition to being sold separately, they're also available in 4-unit "Runner Packs".
I'm told that these models are based on the double sheathed box cars designed by the USRA (United States Railway Administration) during World War I. The double sheathed version was the first widely accepted 40-foot steel underframe box car placed in service. Some 24,500 cars were delivered to 24 different railroads throughout the country.