For years, Mitzi Perdue looked down at her hand and saw history.
The emerald stone on her ring finger told a story stretching back nearly four centuries, to the sinking of a Spanish galleon near the Florida Keys in 1622 and a decades-long effort of a colorful undersea treasure hunter named Mel Fisher to retrieve its payload of gold and silver coins, gold nuggets and jewelry.
It reminded her, too, of her late husband, the chicken magnate Frank Perdue, who received a share of the bounty in return for his investment in Mr. Fisher’s search. He donated most of it, but kept the emerald and presented it to her when he proposed marriage in 1988. She wore it until his death in 2005, when she put it away for safekeeping.
Now, 400 years after the Nuestra Señora de Atocha sank in a hurricane, Ms. Perdue, 81, is putting the emerald up for auction on Wednesday at Sotheby’s in New York City. All proceeds from the sale of the ring, which Sotheby’s says has an estimated value of $50,000 to $70,000, will be donated to support humanitarian efforts in Ukraine, prompted by Ms. Perdue’s visit there this year after the Russian invasion.
“What must it be like for the people who have been there enduring, continuously with no respite, for at least half a year?” she said. “After five days, I wanted to do more. And then I started thinking, ‘What can I do to be most helpful?’ And then I thought, ‘I own something that’s of historic significance.’”
The Nuestra Señora de Atocha set sail from Havana for Spain on Sept. 4, 1622, with a payload that included 180,000 coins, 24 tons of ingots struck from Bolivian silver, 125 gold bullion bars and 70 pounds of rough-cut emeralds mined in present-day Colombia. It had been sailing for only a day when it and another vessel, the Santa Margarita, were struck by a hurricane and sank west of Key West.
Mr. Fisher, who died in 1998, had been obsessed with treasure hunting since reading “Treasure Island” by Robert Louis Stevenson as a boy. After serving in the Army in Europe during World War II and studying engineering at Purdue and the University of Alabama, he briefly turned to chicken farming in California before opening a diving shop in Redondo Beach, Calif. He moved his family to Florida in 1962, lured by the promise of finding offshore treasure.
He and his associates used modern electronics to recover gold and other artifacts from wrecks of a Spanish fleet that sank in a storm off Florida’s Atlantic coast in 1715. By 1969, he had embarked on a search for the Atocha, which he had read about in a book called “The Treasure Diver’s Guide.”
The search for the Atocha’s treasure proved costly for Mr. Fisher. It consumed more than 15 years of his life, and he lost a son and daughter-in-law when their boat capsized and sank in 1975. Finally, in 1985, Mr. Fisher and his team located the wreckage of the Atocha and recovered about $400 million worth of treasure.
“When you’re the first person to see something after three or four hundred years, it just gives you goose bumps,” Mr. Fisher’s son Kim Fisher, who joined his father’s search for the Atocha when he was 12, said in an interview. “And it just makes you want to find more.”
Encouraged by a close friend, Frank Perdue signed on as a patron of the expedition and forged a bond with Mr. Fisher over their shared history of chicken farming. Mr. Perdue was at the pinnacle of his fame as an unlikely TV pitchman — “It takes a tough man to raise a tender chicken” — for his company, Perdue Farms, when the Atocha was found in 1985.
Mr. Perdue was given a share of the treasure proportional to his investment. He gave most of his gems and silver and gold coins to the Smithsonian Institution and to Delaware Technical Community College, where they are on display in an exhibit called “Treasures of the Sea.”
But Mr. Perdue kept two items for himself: a gold doubloon and the emerald.
Mr. Perdue met the woman who would become his third wife at a party in Washington, D.C., not far from his home in Maryland. They courted by phone for about a month — Ms. Perdue was living in California at the time — and the next time they saw each other, she said, he went to his safe and retrieved the emerald ring. They were married in 1988.
“When he gave me the emerald he got from the Atocha, nothing in the world could be more exciting — other than being engaged,” she said.
The emerald was mined in Colombia in the 17th century. Alexander Eblen, a senior specialist of Sotheby’s jewelry department in New York, said it was a pristine example of an old-mine emerald.
“This is a stone that is a Goldilocks stone,” he said, “where it’s a very strong green, a pure green, and also neither too light nor too dark.”
Its estimated value of $50,000 to $70,000 is based only on the condition of the gem, Mr. Eblen said. Bidders at the auction, which are likely to include museums and private collectors, will also take into account its history as well as the cause they are supporting, he said.
Ms. Perdue traveled to Ukraine earlier this year to learn more about human trafficking, a subject that she writes about for Psychology Today. Because of an air raid threat, she spent her first night in Kyiv in a bomb shelter, and it ended up being one of the most consequential experiences of her life, she said.
She thought of her engagement ring, which she had kept in a safe since her husband’s death, and it occurred to her that she could use it to raise money and awareness of suffering in Ukraine since the Russian invasion. She said she did not yet know which organization she would choose to receive the proceeds.
When Mr. Perdue proposed, she initially thought she would wear the ring only for special occasions, but her husband convinced her that it was worth wearing daily. She said she was glad she followed his advice, especially as the emerald moves on to the next chapter in its 400-year story.
“I’d love to shake the hand of the person who gets it,” she said, “and to wish them success and joy.”