PHILADELPHIA — A small Civil War museum made an intriguing discovery while sifting through storage: A document long treated as a photo reproduction of the terms of Gen. Robert E. Lee's surrender appears, upon closer inspection, to contain actual signatures and date to 1865.

Museum officials believe they have one of the three original documents signed by representatives of the Union and Confederacy in Appomattox Court House, Va., on April 10, 1865, a day after Lee's surrender.

The National Park Service historian at Appomattox said it's more likely a souvenir copy signed by the same men at that time — still a significant discovery, he said, even if it's not one of the official copies.

The Civil War & Underground Railroad Museum of Philadelphia has held the document since the early 20th century. It was pulled out of storage and re-evaluated as museum officials prepared to shut down for a move to a new building.

Museum curator Andrew Coldren said that he is certain officials knew what they had when the document was donated, but over time its significance was forgotten because of a lack of record keeping.

In a 1967 inventory, someone wrote "Copy??" in reference to the document. Coldren said it had been glued to a cardboard backing and varnished in what was an apparent attempt to preserve it.

"Old photostat copies from the '20s and '30s are shiny like that, so this is why you'd think this is not a real document," he said.

Coldren said museum officials examining the document recently noticed that the indentation of pens into the paper was visible. He said they also noticed that the ink on the document was darker and lighter in places, as would be expected with the pens used at the time. The lines on a photostat would be of consistent darkness.

"You can see where they're dipping the pen in to get more ink," he said.

Details of the terms and conditions of the surrender were worked out by six men in Appomattox Court House, Va., the day after Lee and Union Gen. Ulysses S. Grant agreed on the broad terms of the surrender.

Three copies were made, according to the memoir of Union Gen. John Gibbon, whom Grant put in charge of working out the details of the surrender.

Gibbon kept one copy, according to his memoir and a letter he wrote to the Maryland Historical Society in Baltimore when he donated his to the society. Another copy was sent to Grant's headquarters and is now in The National Archives.

By process of elimination, the museum believes it has the Confederate copy.

Patrick A. Schroeder, the historian at Appomattox Court House National Historical Park, said that while there were three official copies, "it doesn't mean that there weren't more copies made."

Schroeder, who saw a photograph of the document, said the stationery looks more like the paper soldiers used to write letters to their loved ones than the paper used for legal documents.

He suggests that someone may have made a personal transcript of the document as a souvenir — a common practice at the time — then asked the six men to sign it.

"I would say it's probably a souvenir copy done at the time and signed at the time," Schroeder said.