Our Grinnall Scorpion S3 (#0001) Bought in 2003 after it has been low-speed rolled in the UK,this turned out to be the prototype Grinnall Scorpion S3, and was Mark Grinnalls personal machine for 2 years.
The chassis is more robust than any others I've seen, and has a number of strange features which made it clear to me that it was a pre-production machine. It turned out to be chassis #0001.
We took it to the Sahara, after a wedding we'd been invited to in Tunisia, and it did 5000 km without any trouble. It has a 100bhp BMW K series bike engine.