Ok, so the frame number is 09720. Off to check for Honda stamping son the motor. One thing I noticed is that the key for the transmission keeps sliding out into the cover, have to check that as well.
Like Rick stated , your frame is a 1955 . That , according to our latest registry .
As for the key movement , maybe a drop of super glue might help . If it ever has to be removed , apply high heat .
Or , you could take things apart and wrap the key with aluminum foil and re-install .
Or , you might simply place the key where it's suppose to be and center punch along the key-way to slightly narrow it .
Any of those^ should keep the key from wandering .
Let us know what you end up doing .
Pete .