The units were configured in a highly unusual 2-A1A wheel arrangement (later converted to 3-A1A)[1] mounted atop a pair of road trucks, and equipped with a front swing coupler pilot.

The aft section was divided into two separate compartments: one was used to transport baggage and the other served as a small railway post office, or RPO (the forward door, located just behind the radiator louvers, was equipped with a mail hook).

Six units, accompanied by matching trailing car sets, were manufactured exclusively for the Southern Railway.

The remaining four OP800s were scrapped in 1955; selected parts were retained for maintenance use on other SR F-M motive power.

At least four of these cars had individual names applied to them, including "Vulcan", "Cracker", "Joe Wheeler", and "Goldenrod".