When interior designer Heidi Pribell spotted a dust-covered mantelpiece in the basement of a client's newly purchased home, it was the start of a long relationship.

The ornate white marble mantelpiece, with two caryatids flanking each side, was sitting amid rubble and construction debris. But Pribell, a Boston-based designer and antiques dealer, convinced her client the mantelpiece was worth keeping. That was in 1999.

Fast forward to 2011, and Pribell purchased the mantelpiece -- roughly 6 feet wide and 4 feet high -- from the client. Her "obsession" with the piece led her down a historical rabbit hole in search of its provenance. And this year, more than two decades after the basement discovery, Pribell sold the once dilapidated mantle to the Museum of Fine Arts in Boston for an undisclosed sum.

"It was no secret, I adored it," she says.

It's the kind of story that makes television shows like "American Pickers" and "Antiques Roadshow" so popular. Many people are looking for the next undiscovered masterpiece.

"It's more common than you think," says Ezra Shales, a professor of art history at Massachusetts College of Art and Design. Once-popular works often get thrown out when society's tastes change, he says.

"The cycle of forgetting and then remembering our history is part of the cycle of art history," says Shales.

As a trained antiques dealer, Pribell knew how to qualify items in terms of good, better, best. (Museum-quality artworks are, in general, sold in excellent condition with original fixtures and the like.) This piece, Pribell says, was "exquisite."

"It was all about the quality and depth of the carving," she says.

The mantelpiece also had a story befitting a museum-quality artwork. The Carrera marble mantelpiece, crafted in 1805 in Italy, had stayed in the same building on Joy and Beacon Streets, across from Boston Common, through three different owners.

It was originally commissioned by diplomat and art importer Thomas Appleton, who acquired it for wealthy apothecary Dr. John Joy, whose mansion was on Joy Street. During Appleton's time as a rising diplomat in Europe, he imported many artworks to the United States, including a bust of George Washington that's in the White House.

"He was a true visionary," Pribell says. "He was so sure of his tastes."

The mantel's history of ownership adds to its value. Over the years, it was passed down through the hands of some notable early Americans, including Frederic Tudor, who made a fortune selling ice blocks from Walden Pond. "We relate to decorative art objects and preserve them because of the story of their ownership," says Shales.

Appleton is a big name harkening back to Boston's earliest days. "It's likely the Metropolitan Museum in New York wouldn't have been interested in this piece, but it's a Boston story, so it makes sense for the MFA to acquire it," Shales says.

Pribell has sold other works to museums, including the Chicago Art Institute, Los Angeles County Museum and even Mt. Vernon, George Washington's estate in Virginia.

If you happen to be a treasure hunter, her advice is: Cultivate your own tastes, and get to know the difference between good, better and best.

"Buy what you love," she says. "Become an expert in things that intrigue you."