Arno has informed me that his bike has frame number WM20.96261, and engine number WM20.1515.
Your frame (WM20.96261) was made under military contract S/1048. This was a contract for 15.000 bikes (frame numbers WM20.81818 - WM20.96817). The census number (on the tank) would have been C5129661. Unfortunately the factory ledgers for this contract have been lost, but from the receipt cards we know that the production of this contract started in early June 1943, at 2.000 bikes per month. Which means that WM20.96261 must have left the factory in (approximately) January 1944. As with 99.99% of the WD bikes, it is impossible to find out in which unit it served.
Your engine (WM20.1515) is a bit of a mystery. It was delivered to the War Office on September 13nd 1939, in a batch of 474 motorcycles (no consecutive numbers). It is unknown under which contract these bikes were made, it is also unknown which census numbers they had. This bike may have arrived in France with the BEF, during the phoney war, and may have been abandoned during the Dunkirk retreat. But this is only guesswork.
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