Illustration taken from Sears Roebuck catalog showing available Elkhart low-tension magneto option.
At the very beginning of the Hercules/Economy Model E gas engine era, there were several differences between engines. Additionally, there is one difference that is quite interesting. The early Hercules brand engines with the sheet metal crank guard were available with the more common style Webster magneto as an option. There is no mention made of the Elkhart magneto being an option.
During this same time, the Economy brand engines offered in the Sears Roebuck catalogs were available with the Elkhart low-tension magneto as an option, as noted at the bottom of the illustration taken from a Sears Roebuck catalog. There is no mention made of the Webster magneto being an option. Historically, Sears Roebuck was more conservative and consequently didn't offer ignition updates as soon as Hercules.
Interestingly, the Eco-nomy engines sold by Sears Roebuck apparently were one of the main users of the Elkhart low-tension magneto system. They are seldom seen on other brands of engines.
Glenn Karch is a noted authority on Hercules engines. Contact him at: 20601 Old State Road, Haubstadt, IN 47639; firstname.lastname@example.org