Yep, say my first Rokon in person at the october motorcycle show near Fredericksburg. It looked a bit rough but the guy said it holds spare gasoline in the rims from what I recall. looked pretty sweet..
Another of the original ideas patented by Mr. Fehn was the hollow aluminum wheel, each of which holds 4.5 gallons of liquid ballast or fuel.
From this site, The true history of Rokon motorcycles by Bob Gallagher they have been around since the early 60's.