The UIC-X coaches are the express train coaches of the German Federal Railways, which were put into service from 1952 and were active there for up to 50 years. These coaches had a level of comfort that was unheard of in Europe until then. Until the beginning of the 1960s, they were referred to as üm coaches or m-coaches. New strength regulations made it necessary to modify the wagon body from 1960 onwards. The area at the end of the wagon was made more shock-resistant. Vehicles of the type A 4üm-61 (Am 203) were bought in this version. It had 10 compartments with 6 seats each. The colour of the coach body was 1st class cobalt blue (RAL 5013).