In 1958, the SEAG company built two prototypes of the BTmms 58 derived from the BTms 55, which was designed for four �pa� containers. The cars, one built of light metal and the other of ST 52 steel, could now be loaded with five �pa� containers. This allowed the specific cargo weight to be increased, which in turn allowed the carrier to pay more advantageous rates for freight. The prototype made of steel proved its worth and was further developed to prepare it for volume production, which began in 1960. Over the next six years, a total of 2100 cars of the BTmms 58 class were produced. To simplify dispatching and loading, one end each car had a transition platform located above the buffers or a hand-brake platform in front of the vehicle frame. DB simultaneously exchanged the 35-tonne buffers for heavy duty 59-tonne buffers which were also used from the outset on cars constructed from 1964 onwards. With their V2A containers having a capacity of 5 m3, the medium tank Cars of the types Dikr 602 and 603 were solely designed for the transport of food such as edible oils, juices, and wine. However, also sea water and fuel oils have been documented as cargo for these container types.