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... is one of the coolest looking machines that I've ever seen.

Wolfgang says he bought it in a junk (or pawn?) shop and there are no makers marks on it.

Russian, I bet.

I had an F helicon like that (the other one), sure didn't sound like that when I played it - but from the end credits I guess maybe the lead melody voice doesn't appear in the video.

Yes the helicons might be in the video for mostly visual effect. Rabensteiner is credited with "B-Tuba/Noise/B-Helicon" but I've seen other videos (trio in studio IIRC) in which he plays this helicon. He's a pretty talented player.

I used to have one just like it (see my avatar). Russian - tricky to play, but could sound great.