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
Triumph, BMW, & Kawasaki Sales Spares & Repairs.
Established for over 40 years and run by expert motorcyclists.
Fully authorised workshop.