There were many variations of this type kit from various manufacturers in the teens and twenties. These are now highly collected and valluable in the vintage engine/motor-bike realm.
Antique-Rider and Psuggmog can probably elaborate better, as i'm not well versed in these...
This is the engine that started Briggs and Stratton. They bought the rights from Smith, then built their version of the motorwheel for a while, then adapted the same engine to stationary use. I've got one of each, but none of them running. very expensive to restore. The mag on the smith is a special small mag, they go on ebay for no less that $500. My uncle has a running Briggs, the same one he had as a kid in the 30's. He said he could pull another kid on a bike by holding on to the handlebars, up the Good Sam Hospital hill (Rif knows what I mean). If you look close the engine is hinged at the front so there's no problem going around corners.
Back in the day you could buy also buy a microcar called the red bug, It was a wood chassis car which was also powered by the smith/briggs motor wheel. These were cheap transportation of the depression era.