A reader service card or bingo card is a reply card inserted in a magazine and used by readers to request free samples and literature from businesses who advertised in the issue. Many advertisers are listed on the reply card. Readers circle the advertisers they are interested in and mail back the card to the publisher which then provides their advertisers with the appropriate leads. In 1933, Thomas Register began publishing Industry Equipment News (IEN). IEN became the first publication to include a "bingo reply card."
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Reader service card Wikipedia(Text) CC BY-SA