In 1922 the Deutsche Reichsbahn began to develop a renumbering plan to standardize the numbering of steam locomotives that had been taken over from the state railways (Länderbahnen). Its basis was the corresponding DRG classification system. The first renumbering plan in 1922 envisaged more class numbers than the later plans. The development of this scheme was discontinued because it was seen that there would be problems in practically adopting it. Locomotives that were seen as obsolete and which would therefore soon be retired, were given serial numbers from 7001 after their class number.