Toni Theilmeier has pointed out a few errors in my previous post about the Altenburger brakes in an offlist message. They are indeed Altenburger with a 'U' and not Altenberger with an 'E'. Secondly, they were made in 'Western' Germany (that is what appears on the brakes) and not in Switzerland. The company was set up and owned by the German cycling star of the 30's Franz Altenburger. They were made for many years without any apparent modifications. Initially, they were designed to compete with mid and better quality brakes of the day and ended up being used on low-end city bikes in their second generation of life.