The Opel 4 PS, popularly known as the Opel Laubfrosch (Opel Treefrog), is a small two seater car introduced by the then family owned auto maker Opel, early in 1924. Subsequently, various versions of the little Laubfrosch were produced until it was replaced by the Opel 1.2 litre, itself a direct ancestor of the first Opel Kadett, in 1931.
Initially introduced as the Opel 4/12 PS, and manufactured at Opel’s Rüsselsheim plant, this was the first German car to be assembled on a Ford inspired production line. It was aimed at the lower end of the German auto market, and clearly intended, by the standards of the day, for volume production: it sold well, with approximately 120,000 produced by 1931.
Plagiarism is alleged
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 André Citroën who had initially adopted Henry Ford’s system for the production of munitions, and subsequently applied the technique to production of the Citroën 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 Citroën 5 CV 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. André Citroën nonetheless felt justified in launching a legal action against Opel, and it is not immediately clear just how Opel successfully defended their position.