Evenin' All...
Ta for that 33d6...Is this information solely dependent on the numbers stamped on the gearbox end plate?
An amount the various bits-n-bobs that accompanied this bike including another engine which is a largely complete (but disassembled), this engine does have a completely different magneto / ignition system and only has 3 pole in the flywheel...the manifolds are not chromed like on the engine in the pic...and yep ya guessed it the bit that's missing is the gearbox end plate...which lead me to speculate the VIII-D theory. (Yes the engine in the picture has the 6 pole flywheel...I have since removed the cover plate for a look see)...thinking that the gearbox plate had been replaced...but it has not...the engine in the picture if it had been dismantled it was before 1960 (know Hx to then).
Sorry if this getting a bit drawn out but I was given this bike as being pre-war (I think you have already correctly surmised this).
The Frame number
leans towards this (only has 4 characters...the other frames that came with it all have 5 and the two example of the (post-war) Bennett &Wood head stem logos can still be seen)...but until I can obtain information to corroborate this (proving a tad difficult)...I simple won't know...maybe never know...or will I?
Maybe I can still try dating the Olympic Patrol tyres
...which still hold 20PSI
So open for any Ideas from 'bike-sleuths' with knowledge of Aussie 30's-40's Acmes, welcomed.
Cheers, And ta again