A scrawled name hidden for decades on the back of a painting by Amedeo Modigliani may hold new insights into the mystery surrounding the rightful ownership of a Nazi-looted masterpiece.

Seated Man With a Cane, painted in 1918, re-emerged in the headlines this year when documents contained in the massive Panama Papers leak added fuel to a legal battle for its ownership.

On one side, a retired Frenchman claims title to the painting through his Jewish grandfather, Oscar Stettiner, who he claims was forced to surrender it to Nazi invaders in Paris.

On the other, the billionaire Nahmad family, who masked their current ownership of the Modigliani through an offshore holding company, a joint investigation by the Toronto Star and the International Consortium of Investigative Journalists reported earlier this year.

As the two sides remain locked in battle in a New York court over the fate of the $35-million painting, the latest chapter of the tale unfolded last week.

French television aired an image of a label on the back of the painting — a yellowing remnant from the 1930 Venice art exhibit where it was last publicly displayed.

The name and address of the painting’s “propriétaire” (owner) were crudely scratched out, according to the images contained in a documentary produced by France’s public broadcaster.

But the word “Stettiner” appears to be still visible in elegant cursive script — something emphasized by the documentary makers, who recreated the name through computer graphics.

An address on the line below, also partially erased, appears to correspond with Stettiner’s Rue du Cirque flat in Paris, where he lived until fleeing in 1939 before the Nazis invaded.

“This proves that Oscar Stettiner owned that painting,” says James Palmer, president of Toronto-based Mondex Corp., an international art hunting firm that is assisting Stettiner’s grandson, Philippe Maestracci, in his claim for the painting.

“It proves that it was owned personally … Oscar Stettiner’s name was on the back.”

The Nahmads’ New York lawyer, David Golub, did not respond to interview requests from reporters.

The Star visited Stettiner’s former home and nearby gallery, just off the Champs-Élysées, in March, piecing together the painting’s contested history.

The joint investigation unearthed documents proving for the first time that the painting’s corporate owner — International Art Center (IAC) — is controlled by the Nahmad family, renowned art gallery owners in London and New York who have amassed hundreds of masterpieces valued in the billions of dollars.

Until the Panama Papers revelations, the Nahmads’ identity as owners of IAC was shrouded in the secretive Panamanian corporate registry, complicating the legal process for Maestracci and Palmer.

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In court records, the family initially denied their ownership of the painting.

“International Art Center, S.A., and not anyone else in the world including … Helly Nahmad Gallery, Inc., Helly Nahmad and Davide Nahmad, purchased the painting at auction from Christie’s in London, England, on June 25, 1996,” reads the family’s initial defence filed in court.

In response to reporters’ questions about the documents proving the Nahmads’ control of IAC, their defence shifted to questions about whether Stettiner, who worked as an art dealer in Paris, was the real owner of the painting.

“Very often, the people who are in the provenances are not people that owned it,” Golub, the Nahmads’ lawyer, said at the time. “Lots of dealers have paintings on consignment.”

Documentary evidence gathered by the joint investigation included a program from the 1930 Venice Biennale exhibition that listed the painting from the collection of “sig. Stettiner, (Paris).”

A letter dated April 14, 1930, to the Venice Biennale, written in French, refers to Stettiner as the “owner” of the painting.

A day after publication of the joint investigation — by newspapers in France, Switzerland and Germany, and by the CBC and Toronto Star in Canada — Swiss authorities seized the painting in the Geneva warehouse where it was stored, pending outcome of the dispute.

The latest revelations came after the Nahmads granted the filmmakers access to the painting in the Geneva free port.

“My cameraman really filmed every detail of the painting on both sides,” filmmaker Pascal Henry says in an interview. “And it was thanks to this we found a detail. At the time, we didn’t understand what it was. We looked at it and we said, ‘We’re not experts.’ We didn’t understand the label’s importance.”

He said a closer look this past summer led to the realization that “the name Stettiner fit perfectly into the erased line. I think that all of a sudden we now have a real certainty that the painting belonged to Mr. Stettiner.”

Palmer, speaking from his home in London, said the new evidence — including the image of the label and a translated transcript of the program — will be submitted to Maestracci’s lawyers in New York.

“We’re really striving to get to the truth,” said Palmer. “There have been many obstacles … but I think we’re getting very, very close.”