"It's certainly going to be, perhaps, our most famous flag in our collection," said Douglas Hawes, curator of historical collections with the Augusta, Maine, museum.
On July 2, 1863, the 20th Maine Volunteers, led by Col. Joshua Lawrence Chamberlain, won one of the Civil War's most storied victories when their outnumbered forces defeated Confederate troops on Little Round Top.
Many considered Chamberlain's triumph, highlighted by a daring bayonet charge, a key point in the three-day battle.
Little is known about the journey since taken by the battle flag, which resembles a United States flag with stars and stripes. It did appear in a photograph taken at a Gettysburg reunion in 1882.
Nearly 30 years ago, a flag was given to the Maine museum stuffed into a box slightly larger than a shoe box. The box had a glass top, but it was still hard to see what the contents were. Hawes said for all museum officials knew, it could have been a ceremonial parade flag used early this century.
It was only after a donor was found to pay for the $10,000 cost of conserving the flag that museum officials decided they could take it out of the box to see what they had, Hawes said.
When Fonda Ghiardi Thomsen, owner of Textile Preservation Associates, received the 6-by-6 flag a couple of months ago, she was told it was possibly from the Spanish American War.
But the flag they unpacked looked more like the federal-style battle flags regiments used during the Civil War. The large missing sections seemed to come from shots fired in battle.
During their research, Thomsen and her employees found more and more clues, including seeds in the fabric that were also in Gettrysburg during the time of the battle. The bleeding of dye in the fabric is believed to have come from a heavy rain storm in the days following the battle.
But the clincher was a photograph, provided by Hawes, that showed what appears to be the same flag at the 1882 reunion.
"The condition is indentical," Thomsen said.
She said she was "99.9 percent sure" the flag is indeed the one Chamberlain's forces used on Little Round Top.
"We have more evidence on this flag than most of the other flags that we do," Thomsen said.
Conservation work on the flag included many hours of sewing it by hand between two layers of sheer fabric, which are there to hold the silk cloth in its original configuration.
Thomsen said her company, which works mostly on flags, does not restore but rather conserves, meaning its mission is to save and preserve the fabrics, not to make them look brand new.
"Our goal is to make things last," she said.
The company is also planning to conserve another flag for the museum, that of the 17th Maine Volunteer Regiment. It also has remarkable story behind it, having been for years kept in a museum in Atlanta. The flag was the center of a dispute between Maine and Georgia, and its return to Maine only came after months of negoatiations.