Wikipedia says:
Both the RT 100 and the RT 125 were copied in England during the Second World War. From 1939 Royal Enfield built the RE model, also known as "The Flying Flea". The "Flying Flea" packed in wooden boxes was dropped on parachutes from aircraft for the British ground units. From 1939 WSK in Poland and Jawa in what was then Czechoslovakia also built the RT 125 as license versions.
After the Second World War, no longer protected by patents, the RT 125 became the most copied motorcycle in the world. Many well-known manufacturers copied the motorcycle down to the smallest detail.
In 1946 the Soviet comet K 125 appeared. Also the Harley-Davidson Hummer built from 1948, also under the model names "125 S" for "Super" or simply "Harley-Davidson 125" on the market, the British BSA Bantam, which is a mirrored one due to different customs specifications A copy of the engine has], the Soviet Moskva M1A or the Yamaha YA-1 (the company's first motorcycle) are copies of the RT 125. The rights to replicate in the USA, Great Britain and the USSR were reparations payments after the Second World War; the Zschopau plant was partially dismantled, and production facilities and parts were moved to the countries of the victorious powers.
Other manufacturers who copied the concept of the RT 125 included Moto Morini in Italy with the “125 Turismo” (1946–1953) and Mival and the Hungarian Csepel (1947–1954). There were three manufacturers in Poland who produced copies of the RT 125: SHL with the M02, M03 and M04 models, Sokół with the M01 125 model and WSK with the M06 model. The engine design of the SHL-M11 and WSK-M06 motorcycles is based on the engine design of the DKW motorcycle. The other parts of the motorcycles were developed by the Polish designers. The copies were also consistently developed by these manufacturers and in some cases were built into the 1970s and, as a result of a Polish-Indian cooperation, were produced by escorts in India from 1962 under the brand name Rajdoot until 2005. It was originally a license build of the Polish SHL M11.
There were an estimated 450,000 RT 125s across Germany and more than five million worldwide.
Rudolf