It's most definitely a Viennese Waltz. And it sounds like something you'd have to hunt into Austrian archives to find your answer. It's the kind of song you are likely to hear in an old film, and then you'd have to search for its name that way.
I can envision those old concert halls and dance halls in Austria, like you see in "Sound of Music" and see how this waltz would fit right in.
Good luck. You've got a tough one to figure out. Maybe a poster on this board will save your day by knowing the tune.