I know mine came from Henry because it came with all the original manuals and paperwork with the RC Aero letter head on it. Strange thing about mine is the stock muffler doesn't fit.
I don't know if Henry ever sold any without the plug adapter in it.

The NGK BMR7A sparkplug has a 14mm thread and the CM6 has a 10mm thread.
Below picture of the 14mm to 10mm plug bushing that is in my 45cc.