WM20.63880 was the 448th bike from contract C/12424. It was despatched from the factory on July 14th 1942, destination "Ministry of Supply". The census number would have been C4699977. It is not in the KeyCards, which means that the bike must have been demobbed shortly after the war.
Contract C/12424 was a contract for 8.000 bikes (census numbers C4699545 - C4707544). These are some pictures of factory spec C/12424 bikes. The first three pictures look like Italy, the fourth one was taken during the liberation of Holland.