It looks like a new spin on a Clerk cycle engine, or reid two cycle engine.
The evaporator is hooked to the charging cylinder and is connected to the power cylinder by the cross over tube.
And they have a reversing linkage on the charged cylinder side.
Not a hit and miss engine!
Interesting little do dad.
Thank you Chiptosser, I looked on the internet for the clerk engine and that seems to be it, the reid engine used the clerk idea.
the hit and miss on this Chinese version is electronic and appears to be time controlled rather than anything to do with revs