Earlier this year, a researcher at Concordia University in St. Paul was combing through declassified CIA records and discovered an intriguing stone legacy of the Vietnam War.

At the height of the conflict, CIA Director Richard Helms received a gift from Gen. Vang Pao, leader of the Hmong forces fighting the CIA-led "secret war" in Laos.

It was a massive, ancient sandstone jar, one of hundreds that jut from the ground of the legendary Plain of Jars in northern Laos. At that time, Vang Pao's army was fighting a bloody battle with the North Vietnamese on the plain, with U.S. bombers pounding the terrain and thousands of Laotians on the run.

Through all of this, the general found time to have one of these jars plucked by helicopter and delivered to his American patrons. The CIA had little use for an 1,800-pound megalith, so on Feb. 12, 1970, Helms wrote a letter to the head of the Smithsonian Institution, hoping it would take the artifact off his hands.

"It is my understanding that few of these jars have ever been removed from Laos," Helms wrote in the letter, now archived on the CIA's website. He went on: "Recognizing that the Smithsonian would doubtless prefer to have the Department of State indicated as the donor, I feel confident that we can have arrangements made to handle this, leaving the Agency out of the picture entirely."

At that time, the government was still hiding the CIA's role in the Vietnam War. The Smithsonian secretary wrote back to Helms, accepting the jar as a gift to the American people and hauling it to a warehouse. It has sat there ever since, its public catalog making no note of its unusual origin.

Lee Pao Xiong, director of the Center for Hmong Studies at Concordia, came across the correspondence about the jar while doing research on the CIA's role in Laos. A painting of the Battle of the Plain of Jars, a short-lived military victory for Vang Pao's forces, hangs on the wall of the center.

"I don't know whether General Vang Pao had permission from the King or the Prime Minister of Laos to issue such gift," Xiong said by e-mail. "I wondered if the Lao government now knew about the gift, whether they would want it back."

The Plain of Jars occupies an unusual place in the history of Laos. For a thousand years, starting about 500 B.C., its people carved and hollowed massive chunks of stone and placed them in clusters over the plain. Likely used as burial urns, the largest jars are more than 3 meters high, and the entire landscape has been proposed for a UNESCO World Heritage site.

Xiong's discovery set off a minor frenzy at the Smithsonian's National Museum of Natural History, where the staff was intrigued to learn more about how the jar came into its possession. The museum has 146 million objects in its collections, according to museum spokesman Randall Kremer, but not many of them have such an interesting back story.

For the first time anyone can remember, the jar was brought out of storage in the warehouse, in Suitland, Md., on Sept. 6 and shown to a group of researchers and other visitors, including a former CIA officer, said Paul Michael Taylor, director of the Smithsonian's Asian Cultural History Program.

It looks like a massive potato, with the sides of the jar darkened by lichen where it poked above the earth.

Taylor has no interest in the politics of the jar. Instead, he sees an opportunity to build new community by working with Laotian experts to understand more about the jar and its connection to a lost culture.

"We consider this an American national treasure now," he said. "It's a very important symbol for us of the complex relationship with Laos and its cultural heritage that we have had."

Contact James Eli Shiffer at james.shiffer@startribune.com or 612-673-4116.