In parallel with the design of the 533B 4-10-0, Mikhail Rodnivacek also decided to use the well-proven boiler of the 433E on a ten-coupled locomotive. Since the firebox would not fit above the driving wheels, it had to go behind them, producing the 2-10-2 seen here. Although the 523D was a sound design, it was also orthodox to the standards and practice of the 1930s and was therefore virtually outmoded before it was built.  Within a few years, the delayed Tešlov 533A, an earlier but in many ways more modern design, began to arrive from Krupp and the 523D was immediately outclassed. Construction had been slow anyway, only twenty engines having been placed in service, and the remaining order for ten units was amended to class 533B. Limited by their axle load of 24 tonnes, the 523Ds were restricted to the main line to Čdelectu via Gunerad in the south and to Magane in the north. Furthermore, their small driving wheels caused them to get in the way of faster trains. Despite these disadvantages, the RSR invested in two rebuilds of the 523D. The first, in 1952, involved the fitting of boxpok wheels to improve the balancing and permit running at higher speeds. The benefit achieved was limited, however.

The 1954 rebuild gave three locomotives poppet valve gear in an attempt to improve the steam flow at higher piston speeds. This, too, was but a modest success, owing mainly to the typically poor balancing of the two-cylinder engine. The 523Ds were simply too old-fashioned to benefit from these amendments and it was therefore not surprising that they disappeared quite early, the last one being withdrawn in 1970. All engines of this class ran with Vanderbilt tenders.

Graphics and text © Norman Clubb 2015