Enzo Ferrari reportedly called it the most beautiful car ever made, and the Museum of Modern Art keeps one in its permanent collection, which is not something most sports cars can claim. The Series I E-Type ran from 1961 to 1968 on a 3.8 liter twin-cam six with triple SU carburetors, and the earliest cars have identifying details worth serious money. Read on for what separates a flat-floor car from everything that followed.