The most obvious external change was the steam space cover running the length of the boiler barrel and copied from the ČSD Class 477.0, which lent the locomotives a sleek, modern appearance.

The new boiler made the so-called Reko-01 (Reko is short for Rekolokomotive) into the most powerful German express train steam locomotive.

The new boiler came with a new, welded driver's cab with upholstered seats, side-pull regulator and other improvements to the working conditions of the locomotive crew, as well as an Indusi system.

Because the coupled wheelsets on many engines had to be replaced due to fractured spokes, eight examples (502, 504, 508, 509, 511, 513, 517, 518) were fitted with Boxpok wheels made of cast iron, like those already used in the Soviet Union and the United States.

Such a mishap had been seen at the time as inconceivable because the technical condition of the boilers was checked thoroughly and it was believed that appropriately trained crews - not least for their own interests - would follow the proper safety procedures.

Because the stoker formed a close-knit team with his regular driver and was not used to this situation, a lack of communication led to a shortage of water on the approach to Bitterfeld station.