Founded in 1940 by Karl Altenburger, a professional cyclist, Altenburger GmbH was based in Jestetten, Germany. Jestetten lies in a strange 'peninisula' of German territory that is surrounded on three sides by Switzerland, only connected to the rest of Germany by a single road. One of the hamlets incorporated into Jestetten is Altenburg - presumably the home of Karl's ancestors. The nearest town of any size is Schaffhausen in Switzerland, a mere 5 miles away (bizarrely to the north).
According to Wikipedia, Karl Altenburger developed his first aluminium rim in 1935 and put it into production in 1936, but did not form his company until 1940. In 1953 he sold the company to Aluminum-Werke Wutöschingen based nearby. Altenburger was mainly famous for manufacturing aluminium rims and brakes. Altenburger’s most distinctive product was the Synchron brake which foreshadowed the Shimano dual-pivot design. Production of aluminium components ended at the Jestetten site as recently as 1991.
A company called Altenburger Technologies GmbH, which uses the same basic logo exists today. It is based in Seelbach in the Schwarzwald (125km north of Jestetten) and is an electronics manufacturer.
By the time I came to experience Altenburger products (in the 1970’s) they were irritating items that promised much - but just failed to deliver. In particular their brakes were extremely similar to those of Weinmann (a famous Swiss company) but slightly less accurately made - and missing the tiny feature that was the key to painless adjustment. When UK manufacturers ran out of Weinmann parts they would often fit Altenburger's equivalents as a temporary stop gap - and bicycle mechanics all over the country would groan. Maybe things were better in the 1950’s.
As a naïve Briton, I never made much connection between the German company Altenburger and the Swiss company Weinmann, clearly based in a different country. It was only later that I realised that the two competing businesses were effectively based in the same town - Weinmann was based in Schaffhausen. Their employees would probably bump into each other at the weekly market.
The history of Altenburger derailleurs is a touch obscure. Frank Berto reports that:
I am aware of 5 different Altenburger models: