Prototype monoshock dirt bike was a CZ, both CZ & Suzuki turned it down before Yamaha bought the idea
Shock used in the prototype was out of a Citreon from memory
I think the full story & some photos was on - mxworksbike.com
seem to remember a Belgian guy {Tilkens?} built up a CZ prototype with his idea,
which was a little different to earlier Vincent etc. use of a cantilever swing arm with 2 x small shocks attached near the back of the engine.
the prototype and later Yamaha's used one long shock mounted near the steering head, I assume this was enough of a difference for him to claim and register this as a new design rather than a copy of an old design.