This derailleur, sold in the UK (as this example was) as the ‘GB Altenburger’ and in Germany as the ‘Altenburger Champion’ was designed as a racing gear. This was unusual for a derailleur that mounted on the chainstay - this position was generally reserved for touring equipment. On a number of occasions during the 1950’s, the Altenburger Champion was used by the German team in the Tour de France.
Compared to pull-chain derailleurs the Altenburger is a precise, rigid, parallelogram design. Compared to the Campagnolo Gran Sport it is extremely light and makes extensive use of aluminium.
It has its foibles; the pulley cage pivot, positioned as it is, it does not look as though it has a very high capacity, there are a number of casting flaws in this example, and, unlike the Campagnolo Gran Sport, it only has one adjustment screw - for the high gear position.
For some reason Altenburger did not push sales of this derailleur, preferring to concentrate on their very successful brakes. Nevertheless, it is a sophisticated piece of equipment for its time.