Most of these early automobile signs were enameled or porcelain signs, in which layers of colored, powdered glass were heated and fused onto an iron base. This technique came to the United States from Europe in the early 20th century and rose in prominence until World War II, when the iron in the signs was needed for the war effort. Untold numbers of porcelain signs were recycled for their base metal—after the war, porcelain-sign production seriously declined.
Porcelain automobile signs were made by a number of regional companies, including Veribrite Signs of Chicago. Some were rectangular while others were oval; some had graphics on only one side, while others had graphics on both. Some signs doubled as advertising clocks, designed with functionality in mind so that they would hopefully not be discarded as quickly.
In the 1930s, neon signs became fashionable, so many porcelain signs were adorned with the bright lights to make them stand out at night. In the following decade, with the coming of the war, many sign manufacturing companies switched from porcelain to painted metal and tin. These signs were cheaper to manufacture and ship.
Car companies utilized signs in a variety of places where they would be seen by customers, but the prime locations were repair shops and dealerships. While the messaging in Coca-Cola signs and those of other beverage makers needed only to promise refreshment, automobile signs had to reassure hesitant customers that their prized possessions were about to be delivered into competent hands. One very common Ford sign, for example, bore the slogan “Genuine Ford Parts”; a Buick sign read simply, “Authorized Service.” Some dealers’ used-car lots had to instill confidence without overpromising. Thus, signs in Chevy used-car lots read simply, “OK.”
Ford signs may be the most common among surviving examples, but collected brands also include Buick, Cadillac, Chevy, Dodge, Oldsmobile, Packard, Porsche, and Studebaker.