Here is the original postcard. It reads:
Mein erstgebauter 5 Tonnen Lastenauto Chassie bei der Firma Feyer & Co. Wien Hernalserhauptstrasse No 90
Josef Feyer Robert Rehak
Vogel & Bernhart
Wien, am 14. Oktober 1919
(My first selfbuilt 5 ton truck chassis at the Feyer & Co company, Vienna, Hernalserhauptstrasse 90)
I don't know anything else about it. So it might be that only the chassis was built at Feyer for another truck manufacturer. Additional information welcome, as always.