Now this is trawling the depths of my memory but
I think it was before I was married and that was 1989 and it might have been a while before that
I saw a guy on Tomorrows world I think he was German and he was standing on a pair of curved springs very similar to Bocks and saying he had designed them after looking at kangeroos back legs
He also demoed running and jumping on them so if my memory serves me right it was our own Mr Boeck on his prototypes
I will do some searching an see if I can find out more
Jason