This magnet pictures a late 1930s advertisement for Champion Spark Clubs that promotes the product use in doodlebug midget race cars. The ad text is fun:
"Bunched like hounds on a scent, wheel to wheel and
fighting every inch of the way, a pack of midget race
cars or “doodlebugs” roars and slides ‘round a small race track. In this, one of the fastest-growing sports in the nation, midget race car drivers must have split second response to accelerator. They know their spark plugs must withstand fouling, and pre-ignition due largely to leakage - common to ordinary spark plugs - and eliminated by Champion’s patented Sillment seal. Records show practically every “doodlebug” champion, national and sectional, as well as the majority of all racing drivers, insists on dependable
Champion Spark Plugs. Use the spark plugs
champions use and you will insure all
‘round better engine performance in your car."