Prototype: Union Pacific Railroad (UP) heavy American freight steam locomotive from the former class 3900 "Challenger", in the converted version with an oil tender. Locomotive version with road number 3706 (former coal-fired locomotive, road number 3943). The locomotive looks as it did in the Fifties.
- Completely new tooling, constructed mostly of metal.
- Many separately applied details.
- Striking smoke deflectors.
- mfx+ digital decoder and a wide variety of operation and sound functions included.
- For still more operating enjoyment in the Märklin "World of Operation".