This were the first articulated trams of Austria, based on the trailers type n1 no. 5782 and 5784, with a "floating" middle section and articulation joints developed by Savigliano. These units were rather heavy and slow, so they were withdrawn in the 1970s, but the idea of floating middle sections suspended between two wheeled sections has been taken up in many of today's low-floor trams.
Wiener Straßenbahnmuseum, 2011-06-26.