It’s been over 50 years since Mercedes-Benz showed the C111 concept, a supercar with gullwing doors, stunning design, and an unusual engine. Shown at the 1969 IAA in Frankfurt, the C 111 had four representatives through the 70s—the C111-II, C111-III, and C111-IV—each with different powertrain components, from Wankels to turbodiesels. While Mercedes only built 16…