After WW2 engineer and motocrosser René Mazoyer designed and planned to put into production a 500cc single cylinder motorcycle. He had enough parts to build twelve prototypes but in the end only managed to complete between three and nine unit- depending on the story- some being motocrossers, at least one was a road bike. According to an article in the April 1987 Classic Motor Cycle, one of these bikes was found in a junk yard in 1972, This led the finder to René Mazoyer who knew the former owner of the bike and that led to the finding of the second bike shown here. It does not appear that any more examples of this motorcycle have appeared in the last 30 years. More here.