Help re a small JAP engine

I have acquired a small JAP engine and would like some help to find out the model and date. It is a small 2 stroke and the only marks I can find are the number 20932 and 'JAP London on the magneto backplate. Are there likely to be marks anywhere else? I have calculated its size as 64cc but not sure if this is correct. I measured the diameter and full depth of the bore and dredged up my schoolboy geometry from somewhere to arrive at this figure.
Can anybody help?

jap did a 34cc called the jap 34 or 0
that was one of there smallest they made 64cc ?? not herd of before but i will have a dig and see if they did a 48-50cc seams more fitting
then 76 -98 - 125 ect ect
kev

Thanks Kev, something else that might help is that it has a simple AMAL carb and came with a teardrop shaped fuel tank although that might not be original. Incidentally when calculating the cc do you measure the full bore or just between tdc and bdc?
Alan

After much wire brushing and cleaning I found the details stamped on the crankcase. It is a JAP Model 0 34cc (so much for my maths). The date letter is P which is 1940 although I'm not sure how accurate this is as this was wartime and I doubt any engines were made for civilian use. At worst it will be 1946 which I think is still an early model. Thanks to those who replied.

Rooneysowner wrote:After much wire brushing and cleaning I found the details stamped on the crankcase. It is a JAP Model 0 34cc (so much for my maths). The date letter is P which is 1940 although I'm not sure how accurate this is as this was wartime and I doubt any engines were made for civilian use. At worst it will be 1946 which I think is still an early model. Thanks to those who replied.

p is september 1940 to august 1941 ,so yes its a pre-war lawn mower engine "usually"and the teardrop tank should be fitted over the front and top of engine then later it was a round tank with a flat plate welded to it that was for mounting it on top of the cylinder head
simiar design tank as the villiers slopper engine
and a very simple amanl carb is also correct for this engine "fragile needle inside these and watch how you line it up when refitting the carb top back on
as its very loose and has to be lined up in the little dimple in the bottom or needle will be stuck,bent or tip snapped off ,latter is the common result
kev