Thats a 1952 model year plunger frame and could have been fitted with an M20, 21 or M33 engine. I actually have an M33 with frame number approx 300 higher than yours. My bike was originally shipped to Burma as far as I'm aware.
Thanks for quick reply Ian.
It's a bike for sale and I am doing my homework.
It is advertised as a 1951 and has an M20 engine. I don't have the engine number.
here are you located ?