Bit of Horst Leitner influence there by the looks of it !
I reckon your on track there, I went searching the web the other night, a couple of things I read:
one, said as far as frames went, at the time Honda was copying and trying everything Horst Leitner did.
secondly, I read a published interview where Ron Lechien says basically that both Honda and Kawasaki were both testing and copying everything that they could get hold of from basically any source, anywhere, anyone and each other.
The seller reckonss this is one of three produced?
?
He reckons there is no serial #'s,,,,,,
For my two cents,,,,,,,,I feel it may be indeed one of the real things, but possibly with a history of enjoyment from ongoing use it may have lost its factory 60HP mill. Just like a few have already suggested.
I wonder if the engine has a serial # in the usual place because the above is possibly the case?
??