NEW YORK, NY - SEPTEMBER 08: Joseph Daniels, Presidernt and CEO of the National September 11 Memorial & Museum, speaks at the opening of a display of the American flag that was raised by firefighters above the site of the 9/11 attacks on the World Trade Center in New York on 2001 on September 8, 2016 in New York City. The flag was made iconic in a photo of firefighters raising it on the day of the attacks. The flag disappeared from Ground Zero during the site cleanup and was mysteriously turned into a police department in Washington state two years ago by a man who gave his name only as "Brian". Sunday is the 15th anniversary of the terror attacks. (Photo by Spencer Platt/Getty Images)
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NEW YORK, NY - SEPTEMBER 08: The American flag that was raised by firefighters above the site of the 9/11 attacks on the World Trade Center in New York on 2001 is displayed for the first time at the National September 11 Memorial & Museum after turning up in Washington state two years ago on September 8, 2016 in New York City. The flag was made iconic in a photo of firefighters raising it on the day of the attacks. The flag disappeared from Ground Zero during the site cleanup and was mysteriously turned into a police department by a man who gave his name only as "Brian". Sunday is the 15th anniversary of the terror attacks. (Photo by Spencer Platt/Getty Images)
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Getty Images News Spencer Platt

NEW YORK, NY - SEPTEMBER 08: The American flag that was raised by firefighters above the site of the 9/11 attacks on the World Trade Center in New York on 2001 is displayed for the first time at the National September 11 Memorial & Museum after turning up in Washington state two years ago on September 8, 2016 in New York City. The flag was made iconic in a photo of firefighters raising it on the day of the attacks. The flag disappeared from Ground Zero during the site cleanup and was mysteriously turned into a police department by a man who gave his name only as "Brian". Sunday is the 15th anniversary of the terror attacks. (Photo by Spencer Platt/Getty Images)
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Getty Images News Spencer Platt

NEW YORK, NY - SEPTEMBER 08: The American flag that was raised by firefighters above the site of the 9/11 attacks on the World Trade Center in New York on 2001 is displayed for the first time at the National September 11 Memorial & Museum after turning up in Washington state two years ago on September 8, 2016 in New York City. The flag was made iconic in a photo of firefighters raising it on the day of the attacks. The flag disappeared from Ground Zero during the site cleanup and was mysteriously turned into a police department by a man who gave his name only as "Brian". Sunday is the 15th anniversary of the terror attacks. (Photo by Spencer Platt/Getty Images)
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Getty Images News Spencer Platt

NEW YORK, NY - SEPTEMBER 08: Shirley B. Dreifus stands beside the American flag that was raised by firefighters above the site of the 9/11 attacks on the World Trade Center in New York on 2001 and is now displayed for the first time at the National September 11 Memorial & Museum on September 8, 2016 in New York City. Dreifus's husband, Spiro E. Kopelakis, was the owner of the boat that the flag was taken from by the firefighters on September 11. The flag was made iconic in a photo of firefighters raising it on the day of the attacks. The flag disappeared from Ground Zero during the site cleanup and was mysteriously turned into a police department in Washington state two years ago by a man who gave his name only as "Brian". Sunday is the 15th anniversary of the terror attacks. (Photo by Spencer Platt/Getty Images)
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Getty Images News Spencer Platt