The numbers are definatly
391305 on the frame in two spots, One on the id plate on head stem and also stamped on the frame.
Engine is also U277902.
I would say they have stuffed up in the factory, Bloody germans. Has a glass tank etc.
?
Bike is for sale any body interested PM me, Needs full resto but a good start it also runs. I will try to post up some pictures etc.
Bike is also not mine it's a friends but they are negotible on a reasonable price.
Cya Adam