Austrian Postage Due

Hello! I'm a long(ish)-time CCF poster, and I made an account here because I found a mysterious box full of Austrian stamps in a closet recently. There was also a stack of old postcards (two picture postcards included), envelopes (mostly Europe), and my great-grandfather's Nazi-issued papers (he was a vital tradesman and didn't have to serve). My grandfather kept those to put in the safe-deposit box - the rest are mine.

So here's an interesting one: it's an intact postage due envelope with my great-grandfather's name on it. He lived in the Russian occupation zone, but I think it was sent from the American zone in Vienna (?) with no postage - so twice the deficit was added in postage-due stamps. I'm interested in a rough valuation (probably not much), but I'll never sell any of it.



Anyway, the rest of the contents of that box will hopefully pop up elsewhere on the forum, so keep an eye out!

Wiener Neustadt isn't actually Vienna (Wien) but a town a little south of Vienna. But both were in the Soviet occupied zone. As was Brück an der Leitha, which is also Austria (but I assume you knew that).
Don't have a value for you, but a nice piece it certainly is.

Thank you. I haven't been to Austria in a while, so I was just guessing that since it said "Wiener", maybe it was a "Viennese [zone?]". But I was wrong!