In May 1967, Mazda began selling the world’s first dual-rotor rotary engine car, the Cosmo Sport. It featured the 110-horsepower Type 10A engine (2 x 491cc) equipped with newly developed high-strength carbon-based apex seals, made by permeating pyrographite with aluminum molecules through a special sintering process. This type of apex seal resulted from Mazda’s independent development work and was proven durable and reliable through 1,000 hours of continuous testing. Even after a 100,000 km test drive, it showed only slight wear and none of the chatter marks known as “nail marks of the Devil.”