MADISON (New Jersey) • The borough council meets every other week in a room on the second floor, handling the usual affairs of Madison, a small American suburb, in an unusual space that feels more like a museum.

The floor is a chess board of black and white marble. By the windows is a wooden desk that once belonged to former United States president Abraham Lincoln.

It is an environment where a bust of former French emperor Napoleon, chiselled from marble and weighing 318kg, could blend in.

"Look at this room," said Ms Mallory Mortillaro, hired to take inventory of the art in the building. "You have really nice things hiding among other really nice things."

In 2014, she was 22 with an undergraduate degree in art history when she answered an advertisement for a part-time archivist. Her job was to document the paintings, photographs and sculptures.

She soon got around to the bust, peeking behind it to find something that had apparently been overlooked for 80 years. The markings on the white marble were faint but she saw a signature: A. Rodin.

Her discovery turned into months of research - combing archives, calling experts only to be rebuffed, stumbling into leads - to verify whether the bust was an authentic work of Auguste Rodin, the renowned French sculptor.

Madison is a New Jersey borough of 16,000 people, about 48km west of New York. The borough hall, named Hartley Dodge Memorial Building, was built by heiress Geraldine Rockefeller Dodge as a tribute to her son who died in a car wreck in 1930.

She filled the building with art from her own collection. She also left an endowment, funding a foundation that owns and maintains the art as well as the building.

"When you pull up to the building, it's quite an imposing, stunning building," said Ms Jennifer Thompson, a curator for the Philadelphia Museum of Art and the Rodin Museum in Philadelphia.

"When you walk in, it suddenly makes sense that there might be a great Rodin marble in this place."

Still, Ms Mortillaro initially had her doubts. She found it difficult to believe that the foundation, which had hired her, did not already know the piece was a Rodin.

There had been rumours over the years that the sculpture might be the work of Rodin or his proteges, but there were no records, said Mr Nicolas Platt, president of the Hartley Dodge Foundation.

But over time, Ms Mortillaro was able to map the bust's journey to Madison, working her way back to Rodin's studio outside Paris.

The piece had been commissioned in 1904 by a collector from New York. But it went unfinished until American financier Thomas Fortune Ryan bought the bust after seeing it in the sculptor's studio several years later.

He kept it in his home before loaning it to the Metropolitan Museum Of Art, where it was displayed for more than a decade. After Mr Ryan died, Mrs Dodge bought it at auction.

Another break came when Ms Mortillaro was directed to the Comite Auguste Rodin in Paris, a group that could determine its authenticity. Mr Jerome Le Blay, head of the committee, said hundreds of applications come in each year.

Most works are not authentic. He recognised the Napoleon bust. He knew it existed, but its whereabouts had been unknown for decades.

He travelled to Madison in 2015 to examine the bust. The authentication process was thorough, requiring more research in France. But almost as soon as he saw it, he believed it was genuine.

He was taken by Rodin's sympathetic portrayal of Napoleon, an emperor and conqueror.

"This portrait of Napoleon is a very human portrait," he said. "It's a man who's wondering what he should do and how far he should go."

The bust was authenticated nearly two years ago, but the Hartley Dodge Foundation did not start sharing what had been a tightly held secret until recently. It has said that the bust, which could be worth US$4 million (S$5.45 million) to US$12 million, would be lent to the Philadelphia Museum Of Art.

Ms Mortillaro is now 26 and a sixth-grade language arts teacher, but will return to work at the municipal building. There is still plenty of art scattered throughout the building for her to photograph, measure and investigate.

She could latch on to another mystery to bust wide open.

NYTIMES