Tim Dannels sent along a few images of a cute little 0.13427 cuin. (2.175 cc) sideport spark ignition engine. Bore and stroke are 0.520 in. (13.21 mm) and 0.625 in. (15.87 mm) respectively.  The crankcase is particularly interesting, being formed in one single piece with a perfectly round profile apart from the integrally-formed mounting lugs.  The cylinder installation base is also perfectly round - some nice workmanship to combine those features!  The cylinder base, bypass passage and intake venturi are all very cleanly and competently brazed in place. You’ve got to love the angle at which the induction tube is set! The cooling fins are machined integrally with the cylinder. Finally, the timer appears to be hand-cut from bar stock or thick sheet metal.

Our best guess is that this is a very nice piece of work by a very competent model engineer. However, if anyone out there knows more, please get in touch!