Services for Owners of Classic Motorcycles and Automobiles in Germany
The GTÜ classic car service is a public information and archive system for classic vehicles which includes listings for all major and a good many more obscure German motorcycle marques. There are similar pages available for other European brands.
GTÜ Gesellschaft für Technische Überwachung mbH
Vor dem Lauch 25
70567 Stuttgart
Sadly, the gtue-oldtimerservice.de site is no longer online. Portions of the motorcycle section are available at the Wayback Machine.