It probably is 1936 originally, but with later forks and front wheel. As Adrie says, the petrol tank is 350 size but it has 1937 onwards knee grips so the chances are that someone pranged it and it was sent back to the factory for repair in the 1939 -46 era. A nice bike though.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.