More information: The Champion 3 spark plug drawing has a tracing date of 10-24-26, whth changes through 5-17-28. It is identical to the Champion 2 design except for the added shell skirt and lengthened insulator, designed to extend the plug deeper into the combustion chamber.
The Model "A" Spark Plug by Ed Eaton, Winston Salem, NC
I think it came out the MARC magazine.