TubeNet

http://www.ebay.com/itm/151004386840

Most BBb helicons have 2 back bows. This one only has one. In my eyes there is too much tubing for this one being in F, but I may be wrong.

This one is from the Austrian branch of the Stowasser family.

Klaus

There's quite a bit of large tuning in the valve section but I don't think it's a BBb. Might be an Eb?