Visitors look at the original Star Spangled Banner, the flag that inspired the national anthem, inside a protective chamber at the National Museum of American History in Washington, D.C. In the 1800s, it was not uncommon to snip pieces of the flag to be given as keepsakes. Today the museum traces submitted fragments to see if they are part of the original.

WASHINGTON — If you happen to find some remnants of woven wool in your attic — in red, white or blue and marked Fort McHenry — the Smithsonian Institution would like to know.

Two hundred years after a massive flag was hoisted over the fort in Baltimore that withstood a British attack, Americans from Maine to California may still have fragments from the original “Star-Spangled Banner.”

Not long after the huge 30-foot by 42-foot flag inspired an 1814 poem by Francis Scott Key that would become the national anthem, its caretakers began snipping off pieces.

By the 1880s, about 20 percent had been lost.

Cutting up a flag today could be considered desecration, but back then, the clippings were given away as keepsakes.

“It was such a monumental moment in time that people felt they wanted to hold a piece of that history,” said Jennifer Jones, a curator who oversees the flag at the Smithsonian’s National Museum of American History.

The Star-Spangled Banner is showing its age now, but the Smithsonian carefully preserved it for display. Housed in a chamber that keeps oxygen and lighting very low and temperature and humidity constant, it should last for generations more.

And lest we be too harsh on our forebears, Jones credits the revolutionary-era tradition of souvenir-keeping for maintaining the flag’s value, which “probably led to its ability to survive 200 years.”

At least two families recently inquired whether their fragments might have historical value. Museum conservators are using microscopes, x-rays and other equipment to analyze their weaves, stains and soils to see if they match.