Yes Jan, very interesting. Thanks a lot, amazing that this info is still available.
I didnt have any information about this number or the historie of the motorcycle.
As I wrote, the paper says it was registrated in 1953 as a WM20, 600 cc. As far as I know the present reg system was introduced in Holland at that time. So no more "provincieplaten" (but I'm not sure about that).
Once again; thanks