It was the mid 1970s, and the incentive per diem box car boom was just beginning. A new TrailerTrain iniative called RailBox aimed at streamlining boxcar pooling and availability. Pullman Standard was a significant builder of many of these cars. The 50’ outside post, non-terminating end box car, became the foundation for new per diem cars built in the 1970s. Some of the RailBox 50’ PS cars started to be distributed to partner railroads in the late 1980s. These models can still be seen today in the modern railroading scene.