In the early 1970s, the older types of railway mail cars could hardly be used profitably anymore. The first new cars built in 1952/53, with a maximum speed of 120 km/h, were also only limited in their usability. Therefore, in 1973, the Deutsche Bundespost commissioned new railway mail cars. By 1976, 200 cars were produced, referred to as "Post mrz." Originally approved for a maximum speed of 140 km/h, they were modified and upgraded for 200 km/h starting in 1979. This allowed these cars to operate in IC and EC trains as well. The 200 km/h postal IC trains were the main area of use for these cars, which were initially painted green and later ocean blue/beige, until the mid-1990s. After the decommissioning of the mail cars, some were sold to private companies, including RailAdventure, which uses these cars as coupling cars for vehicle transfers.