Henk, there is an ebay auction in Nashville, Tennessee USA for a WM20 frame and bits. The frame number is WM2079806 and the license number is 01YE71. If these numbers are a pair from one bike, we now know the location of one more old soldier.
WM20 79806 and license number 01YE71 are indeed a matching combination. This BSA has been used in Germany a BAOR and many of these ended up in the USA.
J Woods & sons have a complete WM 20 coming up in the sale of the Mike Harper collection next week.
Think there was a couple of other war birds in the collection and some tastey parraphanlia