There´s a two page article about the two machines in the German magazine Rad&Kette 2/2013 (meaning "Wheel&Track";
www.rad-und-kette.de), which appeared on 22nd March (we subscribers got it some days earlier though
). According to the article, it was actually the company making the original tracked dumper who approached ScaleArt to have an operating model made for fairs and for learning purposes. Had it not been for this, I don´t believe ScaleArt would have made the model at all.
Stefan