The Vaillante Mystère is a disguised Vaillante prototype, used by Racer X in the 1960 season. Its non-prototype form is the successor to the Vaillante Grand Prix, in use since early 1959. This car is the result of Jean-Pierre Vaillant designing a car that would be able to compete to the ever advancing competition. Fearing his father's reaction, however, he disguised the car in black and raced during the 1960 racing season, proving both Team Vaillante and the rest of the competitors it to be a formidable car.
As Jean-Pierre has stated matter-of-factly, the reason the Marne Grand Prix was lost was not due to the car's capabilities, but his; Michel being the better pilot of the two, Jean-Pierre just couldn't win of the Russian Zvezda's. Subsequently, Michel uses this car to win the Italian Grand Prix in Monza.