Historically Important German Cars: The 1924 Opel Laubfrosch or "Tree Frog" -- the first moving assembly line car in Germany

The 1924 Opel is one of the most important cars in German Automotive history. It's green color is at the origin of its "tree frog" nickname, but its importance is because of the way it was made, the numbers made, and the controversy over its design related to a very similar looking Citroen model. A car with 4 taxable horsepower, approximately 120,000 were made by 1931.


Opel’s Rüsselsheim plant may have contained the first automobile production line assembly system in Germany, but the first automobile production line in Europe had been created by Andre Citroen who had initially adopted Henry Ford’s system for the production of munitions, and subsequently applied the technique to production of the Citroen Type A. It was not merely the production system that Opel took from Citroën. The two-seater Opel 4 PS when launched in 1924 bore an uncanny resemblance to the little torpedo bodied Citroen 5CV which had been launched in 1921. Sources differ as to whether Opel purchased the right to assemble the Citroën under licence, or merely copied the design.
There were differences. The Opel’s wheelbase was longer by 5 mm and the look of its radiator was different. The early Opels were mostly green whereas the early Citroëns were mostly yellow. Under the skin, the Opel had a twelve-volt electrical system at a time when most cars (including the Citroën 5 CV) used a six-volt system. And the Opel’s four-cylinder water-cooled engine size was larger, at 951 cc, than the Citroën’s 856 cc.