I had no idea what these were when I found a whole box-full at the swap meet. I just knew I loved the artwork. If you're not familiar with the world of amateur radio, allow Wikipedia to enlighten:
"QSL is one of the Q codes used in radiocommunication and radio broadcasting. A Q code message can stand for a statement or a question (when the code is followed by a questionmark). In this case, QSL? means "do you confirm receipt of my transmission?" while QSL means "I confirm receipt of your transmission". Some also take it to mean "Query Station Location".
QSL cards confirm either a two-way radiocommunication between two amateur radio stations or a one-way reception of a signal from an AM radio, FM radio, television or shortwave broadcasting station. They can also confirm the reception of a two-way radiocommunication by a third party listener. A typical QSL card is the same size and made from the same material as a typical postcard, and most are sent through the mail as such."
These ones probably date from the 1960's to 1970's by the look of things.
Some folks did the art themselves while others hired local talent, often an employee at the local print shop. Using a wild array of fonts, hand-drawn lettering, clip art, photograps, cartoon characters and anything else that caught their fancy, these cards were mailed between ham radio operators as confirmation of communication between them.