Two prototypes of the class 06 were built in 1939 as the only German steam locomotive with a 4-8-4 wheel arrangement for particularly heavy express trains on mountainous lines. They got the boiler of the class 45 and were streamlined. As with the 45, the boiler with the overly long tubes caused problems. There were also occasional derailments in narrow switches. Due to the Second World War, there was no series production and even after the end of the war, no new locomotives were based on the 06 due to a lack of demand.