1920–1939 thumb|Opel RAK.1 – world's first public flight of a manned rocket-powered plane on 30 September 1929 thumb|Opel Admiral convertible (1937–1939) thumb|Opel Kapitän (1938–1940) In the early 1920s, Opel became the first German car manufacturer to build automobiles with a mass-production assembly line. In 1924, they used their assembly line to produce a new open two-seater called the Laubfrosch (Tree frog). The Laubfrosch was finished exclusively in green lacquer. The car sold for an expensive 3,900 marks (expensive considering the less expensive manufacturing process), but by the 1930s, this type of vehicle would cost a mere 1,930 marks – due in part to the assembly line, but also due to the skyrocketing demand for cars. Adam Opel led the way for motorised transportation to become not just a means for the rich, but also a reliable way for people of all classes to travel.
1920–1939 thumb|Opel RAK.1 – world's first public flight of a manned rocket-powered plane on 30 September 1929 thumb|Opel Admiral convertible (1937–1939) thumb|Opel Kapitän (1938–1940) In the early 1920s, Opel became the first German car manufacturer to build automobiles with a mass-production assembly line. In 1924, they used their assembly line to produce a new open two-seater called the Laubfrosch (Tree frog). The Laubfrosch was finished exclusively in green lacquer. The car sold for an expensive 3,900 marks (expensive considering the less expensive manufacturing process), but by the 1930s, this type of vehicle would cost a mere 1,930 marks – due in part to the assembly line, but also due to the skyrocketing demand for cars. Adam Opel led the way for motorised transportation to become not just a means for the rich, but also a reliable way for people of all classes to travel.