When the Bosnian-Herzegovinian State Railways put the route over the Komar Pass into operation as the next 2 ft 6 in rack railway after the Narenta railway in 1894, more powerful rack locomotives based on the Abt system were needed. The basis for the development was the class IIIb4, which had three coupled axles and a single-axle Klose supporting tender and was already in use on the Narenta railway. Adding a second axle under the supporting tender allowed not only to increase the supplies, but also to carry the load of a heavier boiler.

Technically, the locomotives shared many similarities with their predecessors. Due to the small gauge, an outer frame was still used, and the cylinders of the rack drive were still on the inside. In adhesion mode, still the the third coupled axle was powered. There were minor differences between the individual production series, for example the grate surface was initially reduced from 1.66 to 1.58 square meters. Also, some engines were oil-fired to improve visibility in tunnels. Compared to the 60 tonnes of the IIIb4, it was now possible to tow 80 to 90 tonnes on the six percent gradient, since the power was now 300 hp instead of 250 hp. With two pusher locomotives, train weights of 240 tonnes were even possible.

Sectional drawing with dimensions

Die Lokomotive, August 1940

They replaced the IIIb4 on the Narenta railway, so that these were relocated to the route over the Komar Pass. But the IIIc5 was soon used there too. Since the two Mallet locomotives IIIb5 Nos. 751 and 752 had not proven themselves, additional engines with Klose supporting tenders were purchased in the years 1911 to 1919. This brought the number to 38, making it the most built rack locomotive. At the Yugoslav State Railways they were listed as class 97. The use of these locomotives ended there with the gauge change on the Narenta railway. The route over the Komar Pass was finally closed in 1975, which meant the end of the service life of the IIIc5. Four pieces are still existing today.