At first glance, Rodnivacek's decision to build new 2-6-2 tender locomotives just after the class 423A and 423B 4-8-0s and 4-8-4Ts had appeared is puzzling, to say the least. At this time, the earlier Tešlov 2-6-2s of class 333A were in the process of being withdrawn and it is hard to see a sensible sphere of operation for the 333Bs. Also, the 1950s were a time of decline for steam all over Europe and it was only thanks to Rodnivacek that the RSR postponed the decision on new forms of motive power till 1980 and the rest, as we say, is history. Against this background Rodnivacek was already planning the next generation of steam power but needed in the short term a faster version of the 423A. The 333B consisted almost entirely of standard components (much in the manner of the Turkish 57 class 2-10-2s), simplifying construction and reducing design effort to a minimum. In total, eighteen engines were built, some running on boxpok wheels (and becoming class 333BB) and some attached to Vanderbilt tenders. All four variations were to be seen. The highly advanced and sophisticated locomotives of Rodnivacek's successor, Jochann Ketterik, soon outclassed the 333Bs and the last survivor was withdrawn in 1977.

The 1950s trend towards poppet valves almost passed the 333Bs by. In the event, it was possible to amend the order for the last six engines, making these class 333BC. The superiority of the poppet valve was not able to prevent these locos from sharing the fate of their piston-valved sisters, however.