The Use of the AFPA Recycling Symbol
Products made from 100% recycled fiber should use either one of the following symbols:

If the paper used is made with less than 100% recycled fiber, the symbol should be accompanied by a legend identifying the total percent of recycled fiber. An appropriate legend might read "XX% total recycled fiber content."

The U.S. EPA defines recycled fiber to include both pre- and post-consumer fiber.

Where did the Recycling Symbol come from?

In 1970, the year of the first Earth Day, the Container Corporation of America (which is now part of Smurfit-Stone Container Corp.), at the time the nation's largest producer of recycled paperboard, sponsored a contest for a design that symbolized the recycling process. The design was to appear on the company's recycled paperboard products.

The contest, which was judged at the 1970 International Design Conference in Aspen, Colorado, was won by Gary Anderson, at the time a senior at the University of Southern California. His design, three chasing arrows, was based on 19th century mathematician August Ferdinand Mobius' discovery that a strip of paper twisted once over and joined at the tips formed a continuous single-edged, one-sided surface. This is why we sometimes call the recycling symbol a Mobius loop.

Source: American Forest and Pulp Association