Commencing in 1924 the SAR took delivery of 600 O wagons in knocked-down form from American Car & foundry, they were assembled at Islington workshops. These were rivetted construction with full height pressed side panels. During 1927-1928 Islington workshops built a further 150 cars to a similar design. In 1954 the SAR built a further 100 wagons but with all welded construction and three quarter height pressed side panels. These wagons fulfilled a variety of traffic roles and all the rivetted wagons were progressively rebuilt to the same external appearance as the later series of wagons. The wagons are all 43′ long and have four double doors.
The model was initially designed and tooled by Eureka Models, Phoenix have revised the design and expanded the range to cover a larger variety of prototypes.