The 1953 GM XP-21 Firebird was the first gas turbine car, inspired by the much-admired and new technology of aircraft. Entirely unsubtle, it was truly a jet plane on wheels, and proved General Motors could reach far outside the box. But not every concept car was meant to leave the research lab. The 1955 Mercury D-528 Beldone was never even given a proper name, and lived a life of being poked and prodded like a laboratory rat.
