The machine originally bearing engine and frame numbers W10299 was supplied under contract C5612 and carried WD serial (census) number C4155467.
However 10299 (perhaps followed by 'N4') is sometimes seen as a casting number on saddle lugs and seems to have been taken up as the frame number from time to time.
W34868 was fitted to a frame with matching number built under contract C7353. It would have displayed C4394894. Although a 1940 contract, only about 2500 had been delivered by December so actual build date is likely to have been the first half of 1941.
My personal feeling, if restoring a bike with mis-matched components is that it may be more appropriate to use a serial number from a 'rebuild' series or if building to an authentic early specification, perhaps to base it on the engine number which is much more visible on the completed bike.
Thanks for the information, I have an old log book which shows the frame number as registered for the road in 1948, so what ever changes were made was befor this time, what would have been the contract year of the frame number if it was correct?
C5612 commenced delivery in March 1940 (W7000) and seems to have been completed at W10999 around mid-June.
It would have been almost to the pre-war specification (early carrier / no panniers and rubber footrests etc.) The side-mounted speedo had been adopted by that time.
