After the Deutsche Reichsbahn had been founded in 1920, in 1921 all goods wagons types with the same or similar roles were grouped into so-called class districts. These were named after cities that were the headquarters of a Reichsbahn division or, later, other cities too. Work on re-lettering and renaming the wagons began in 1922 and was largely completed by 1924.
Class districts of the Deutsche Reichsbahn from 1921