if these are the only papers you've got you should definitively get some legal ones. fortunately, this is quite easy for pre-1992 simsons. all you have to do is write an email to the kraftfahrtbundesamt ( firstname.lastname@example.org). this email should contain:
*your name and adress
*exact type of bike (in your case KR51/2E if it's the same scoot as above)
*VIN (to be found stamped into the frame under the seat)
*year of manufacturing
*your phone number for questions that may occur
normally, the processing only takes a few days. then, the mail guy will ring at your door and want approx. 25€ for your fresh paperwork - simple as that!