September 1943, but there is a discrepancy I need to sort on the dating certificate from the Matchless owners club as 2 digits of the frame number are the wrong way round so there is a difference of 4000 bikes, although still part of contract 4555 which was a total of 8000 bikes and this was late 43.
There is a plate on the tool box that has a Chassis Contract number and catalogue No, in some cases these come from different bikes or are original to the box but have been fitted to another bike, in this case everything checks out thanks to Roy on the HMVF (Historic Military Vehicle Forum) who has some very nice vehicles and been a great help.
With the info he provided, I now have the Census number as seen on all or most WD bikes with a C prefix.
Did a temp repair on the oil supply pipe yesterday just to get some oil around the system and to check the pump, I wanted to kick it over to see if the magneto was doing its job as it looked a bit neglected, with a good kick produced a nice spark so a quick clean of the carb and a temp fuel tank rigged up should get a start.