While the RSR was still pondering where to order the new 2-10-2s Tešlov had designed, work had already started on their passenger counterparts, the class 433D 4-8-2s. Henschel, of Kassel, who had free capacity where another order (from Portugal, evidently) had been cancelled, were able to fit the RSR job in. A total of 60 of these superb engines, which were to revitalise the RSR's passenger traffic as the 533As would later do with the goods services, was delivered during 1950 and 1951. Unfortunately, owing to a misunderstanding in the drawing office, which led to the assumption that the loading gauge could accommodate the extra height of the chimney extension common in German practice, the 433Ds were too tall as built and had to be confined to major routes in the northern plains. After the embarrassment of the 434A, the RSR knew better that to complain to Henschel.

Starting in 1955, most of the class received new tapered boilers, which despite a slightly reduced heating surface were thermodynamically superior, becoming class 433DD. Their height was also reduced to fit within the general RSR loading gauge.

The positive experience the RSR was achieving with poppet valves led also to their application to the 433DDs. As they passed through the works from 1957 onwards, all engines were fitted with the new valve gear, greatly enhancing their performance and efficiency.

In 2000, all fifty-nine 433DDs (no. 433DD.034 was badly damaged in an accident at Nestavor in 1957 and had to scrapped - without having received its poppet valves) were still in service and making a sizable contribution to the RSR's passenger moving efforts, sharing the top links with the later 4-8-4s. Withdrawals began in 2002 and have proceeded at a steady pace, leaving just nine engines in service as of January 2008. No. 433DD.017 has already been set aside for preservation in working order. In their time the 433DDs were, it seems, more popular with the enginemen than later designs, owing to their easy steaming and roomy (although admittedly draughtier) cabs.