Hello Pete

OOH ... that is a super-rare 320-07.
This is the first 4-stroke Pope. I have never seen one.

It cannot date to 1956, but it is earlier than you think Pete.
It would date from between 1960 to early 1962. No later.
That odd air cleaner is all Clinton... and with a catcher!

Have a look at Part One Chassis here:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=60790

Hope this helps.
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JACK