My Japanese bike serial number would not be relevant to the TT mystery. If you want to solve the mystery, Europe will be your best bet. The post above mine had a good suggestion. Also contact the bike shops located in and around Germany. You might get lucky. My Asian Expert has a faded sticker from the Japanese shop that originally sold it. I looked them up and they are still in business. I also have a Condor that was purchased in the early 70s from the shop in England. They are still in business as well. You might get lucky.