For 75 years, the large marble bust sat in the corner of the Madison, N.J., council chambers, slowly gathering a faint brownish haze from decades of tobacco smoke.

There were strong suspicions that this was not just any bust, but a genuine Auguste Rodin rendering of Napoleon. For one thing, it was apparently signed by the great French sculptor.

"You said, 'Uh huh, Auguste Rodin — right,' " said Janet Foster, a Madison resident and trustee of the foundation that owns the bust and other artworks in the Borough Hall. "Why would that be here? But it was!"

On Wednesday, the borough announced that the sculpture had been authenticated by Jérôme Le Blay, an expert dispatched by the Rodin Museum in Paris.

The kind-of-lost bust will now be headed to the Philadelphia Museum of Art on an extended loan, although the details were still being worked out as of Thursday afternoon.

Jennifer Thompson, head of the Art Museum's department of European paintings, said the bust will be installed at the museum in Gallery 155, joining Rodin's John the Baptist Preaching and Helmet-Maker's Wife. All three works will be on display in time for the museum's observance of the centenary of Rodin's death, Nov. 17.

Thompson is excited about the loan.

"It is a well-documented piece," she said Thursday. "There is a great photo of Rodin next to it, leaning on it."

The bust was acquired by Geraldine Rockefeller Dodge in 1933, and it joined her burgeoning art collection. In 1935, she gave the Rodin and many other artworks to the Hartley Dodge Memorial, which she named for her late son.

The art was placed in the stately Borough Hall that Dodge built for Madison to use as its municipal building.

Foster, trustee of the memorial, said Dodge neglected to pass along any documentation of the art. There was no way to prove or disprove whether the bust was by Rodin.

In the winter of 2014-15, however, the foundation hired a graduate student from nearby Drew University, Mallory Mortillaro, to catalog the collection. Mortillaro immediately zeroed in on the bust.

"It's a big hunk of marble," she said. "I mean, this is Geraldine Rockefeller Dodge. She's a Rockefeller. I knew we weren't dealing with random bits from somebody's attic."

Mortillaro contacted the Rodin Museum in Paris. A few months later in 2015, Le Blay walked into the Madison council chambers.

"He walked in and saw the bust and said, 'Oh! There you are!,' " Foster recalled. " 'I wondered what happened to you.' "

According to Foster, the Rodin Museum in Paris possesses a plaster model of the bust but did not realize Rodin had actually carved it out of marble.

"They knew of the piece," Martillaro said, "but they didn't know where it was."

Recent research has shown that New York collector John W. Simpson commissioned the bust in 1904. Rodin didn't get very far with it, and the unfinished piece was acquired by another collector, Thomas Fortune Ryan, in about 1908. Rodin completed the bust in 1910. It was on loan to the Metropolitan Museum of Art in New York from 1915 to 1929, and Dodge acquired it four years later.

The bust — which is officially called Napoleon enveloppé dans ses réves or Napoleon wrapped in his dreams — will remain in council chambers for the moment, and will leave in a couple of weeks for Philadelphia.

"It's part of the fabric of the building," Foster said. "But our capacity to show it is limited."