It was primarily a bread promotion employed by bakeries. However, it was also utilized by laundries too. Pictured below is the front cover of a four-page brochure for the Snow White Laundry in Philadelphia. It introduced kids to the Jingle Club and included the mail-in perforated card so they could join. In the next post, we'll see the book and a few of the Jingle Cards distributed by this same laundry.
Image via Heritage Auctions.