Chrysler Thunderbolt (1941 concept car)

The retractable hardtop starts here. The Thunderbolt's one-piece metal roof retracted electrically into a space behind the seat at the flick of a switch, giving a closed coupe and an open roadster in one body, and its headlamps hid away when not in use. Folding metal roofs took decades to become a common showroom option, but the trade-off they solve, the quiet and security of a coupe with the fresh air of a convertible, is exactly what this car demonstrated in 1941. Only five were built, so seeing the idea work at all on a prewar car is the point: the smooth, enveloping body looks like a styling exercise, while the roof is a genuine engineering preview.