The first train to arrive to Niš from Belgrade was on 4 September 1884. At that time it was considered a great achievement, as Serbia was under pressure to finish the railway within a tight deadline, and with the help of Austro-Hungarian loans and French construction, the deadline was met. The line started operating regularly from 15 September 1884. At the time, the full journey from Belgrade to Niš took almost 10 hours. The railway was operated by the French company until 21 May 1889, at which point Serbian Railways took over the operation. Niš was also home to a railway workshop to service wagons and locomotives. Since 2013, Serbian Railways is undergoing modernization of its aging infrastructure and improving large parts of its main lines, in addition to introducing new trains.
From what we could gather, these locomotives were used mainly for freight trains which were taken out of service around the period of World War II, but information about them is scarce. The cache is a small magnetic container, tread carefully.
For more information:
http://starinis.rs/dolazak-prvog-voza-u-nis/
https://en.wikipedia.org/wiki/Serbian_Railways