Call it a rivalry for the record books.

Comerica Bank and San Diego County Credit Union have battled over the past two years to claim the Guinness World Record for "Most Paper Collected in 24 hours." The record has been broken five times since 2012, and each bank has secured it twice, a Guinness spokeswoman said.

For the financial institutions, the road to Guinness fame and glory was paved with tiny scraps of paper. Comerica and the credit union won their respective titles by hosting community paper-shredding events designed to raise awareness of data security and sustainability.

San Diego County Credit Union, the reigning world champion, took the title in July by collecting and shredding 428,998 pounds of paper. Before that, Comerica held the record by bringing in 401,925 pounds in April.

But who's counting? Other than the Guinness-certified judges, of course.

Comerica got involved in document shredding in 2007, after working with a local reporter on a story about identity theft, said Kyle Tarrance, a vice president at the bank. "We had thousands of people show up year one, and the event has just grown," he said in an interview, adding that demand for the service "clearly exists."

A few years ago, the bank began noticing that collections were getting so large that they began weighing the paper bales compiled by Iron Mountain, which co-hosts the annual event.

Comerica in 2012 invited a Guinness judge to its annual "Shred Day" in Dallas. The judge was responsible for "making sure the scales were calibrated properly" and monitoring the Dallas event from start to finish.

The result? Comerica claimed the world title, collecting enough paper to stack more than two and a half miles high.

Comerica plans to hold its next "Shred Day" on Oct. 11 in Phoenix. It will be the first time the bank hosts the event in Arizona. Tarrance said a Guinness judge will not be present. "We're not trying to set any records," he said, noting that their priority will be on working with the community.

San Diego Credit Union did not respond to a request for comment. You can find its current world record, however, listed somewhere between "Most People Wearing Paper Crowns" (14,621) and "Largest Folded Paper Boat" (33 feet).

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