I don't think this story is genuine. 1892 is way, way, way too early.
Back then Serbia was part of the Austro-Hungarian Monarchy. It is a known fact that in 1894 there were four motorcars in the Monarchy - none of them in Hungary and to my knowledge not one in Serbia.
Theodor Liebig used two Benz cars in the Czech part of the Monarchy, I know a Benz in Austria but I can't recall the fourth one.
And I just remembered something: there was not a World Fair in 1892. There was one in 1889 and another in 1900.
After three years of research, I can say that the first internal-combustion engined car probably arrived to Hungary between July and September, 1896. So a car in Serbia in 1892 looks a bit surprising to me.
And one more thing. If anyone from Serbia would like to have confirmation one way or the other, you should go to the National Archive in Austria. There's a bunch of materials on a Benz which someone wanted to import to Trieste in 1895. The Austrian tax authorities dismantled the car, and its engine was taxed as scrap iron, while the shell was taxed as a carriage. Naturally he appealed against the decision, saying a new category, "motorcar" is needed. The finance ministry asked all member states of the Monarchy about their experiences in applying custom's duties on automobiles. I recall that there was a letter from either Bosnia or Serbia, but I was not interested in it, I focused on the reply of the Hungarian ministry of finance