When Bela Šahlmeti took over the reins from the suddenly-deceased Belčamin in 1919, he inherited a fleet of locomotives that, after the vagaries of the First World War, were quite badly run down (aside from those machines - mainly the D6A 4-8-0s - produced after the end of hostilities). It fell to Šahlmeti, therefore, to restore and modernise what there was. The first step taken was the rebuilding of the Belčamin D8 0-8-0s. These engines, of which 27 units had originally been built, were provided with new boilers and leading axles, both of which improved their power and usefulness. The first of these emerged from Akohniçe in September 1921, followed by another 14 by the end of the year. In their new guise, they outlived their unrebuilt sisters, the last one being lost to sabotage late in the Second World War. In 1920 the entire locomotive stock of the RSR was reclassified, the D8s becoming 423Bs and the rebuilds - logically enough - 423BBs.

As good as the 423BBs were, Šahlmeti was looking for ways to improve their starting ability on the gradients of the southern highlands. To this end, he designed in 1924 a booster tender, which was attached to one of these engines, thus creating class 423BD. The new tender turned out to be mixed blessing. The additional 9,000 lbs of tractive effort were tractive effort were undoubtedly useful but the outside cylinders on the short-wheelbase bogie caused severe hunting and resulted in one or two derailments; the exhaust steam, being led through the water tank, caused this to heat up almost to boiling point and stopped the injectors from working properly; the crews were annoyed at having to maintain an extra set of very delicate motion; and the axle journals ran hot with almost comical regularity. All in all, it seems Šahlmeti repeated the saga of Sturrock's steam tender on the English Great Northern Railway in uncanny detail. Needless to say, the tender was taken out of service within a year (in fact, the engine never carried its assigned new number). The tender chassis (bereft of its motion) was used in the works for transporting boilers and other heavy items and finally succumbed to the general wartime drive for scrap metal in 1943. The locomotive is shown below.

Text and graphics © Norman Clubb 2012