JERUSALEM — The grandchildren of one of the earliest Jewish victims of the Nazis are laying claim to a jewel of Israel’s top museum: the world’s oldest illustrated Passover manuscript.

The descendants of a German Jewish lawmaker say the famed Birds’ Head Haggadah, a medieval copy of the text read around Jewish dinner tables on Passover, was stolen from their family during the Nazi era and sold without the family’s consent 70 years ago to the predecessor of the Israel Museum in Jerusalem — an act the family calls a “long-standing illegal and moral injustice.”

The medieval manuscript, which tells the biblical tale of the Israelite exodus from Egypt, has long vexed scholars with its peculiar drawings of Jewish figures with bird-like heads. Now, a new page in the manuscript’s history is being written, as a high-profile American attorney who restored looted masterpieces by artist Gustav Klimt to their Jewish heir — a courtroom drama made famous in the recent Hollywood film “Woman in Gold” — is taking on the case.

The manuscript is currently displayed behind glass in a darkened room at the special exhibit at the Israel Museum ahead of the weeklong Passover holiday, which begins Friday. The family wants the manuscript to remain at the museum, but it demands the museum pay compensation and rename the manuscript after the family, or face a lawsuit.

“We want a compromise,” said Eli Barzilai, 75, who lives in Jerusalem.

He is leading the restitution demand in Jerusalem on behalf of his cousins in the United States and Berlin. He said the manuscript is so rare, its value is priceless.

The Art Newspaper, which first reported the ownership claim, said the family is seeking “less than” $10 million, but neither Barzilai nor the family’s lawyer would cite a figure to The Associated Press.

“If we go to court,” he said, “there’s no turning back.”

Barzilai, who is spending Passover on a tour of China with his wife, said his lawyer and the Israel Museum had exchanged documentation regarding the Haggadah, and that Barzilai would meet museum staff for the first time in May.

The museum said in a statement that it “looks forward to meeting with Mr. Barzilai, following its several suggestions that he do so, and to learning about whatever new information and documentation he has and to sharing what the Museum knows with him.”

In an email exchange provided by Barzilai’s lawyer, the museum’s lawyer acknowledged the Marum family’s ownership of the Haggadah “for a period of time up until 1933.”

Written in southern Germany around 1300 by a scribe identified only as Menahem, the Bird’s Head Haggadah has long been a riddle. Marc Michael Epstein, Vassar College professor and author of the book The Medieval Haggadah, called it “as mysterious as the Pyramids of Giza, the monoliths of Easter Island, or Mona Lisa’s smile.”

Much of the enigma surrounds its strange illustrations of Jewish figures. Epstein believes the heads on the figures are those of griffins, a beloved mythical creature, and the drawings were meant to offer a positive representation of Jews while skirting a biblical prohibition against depicting human likenesses.

Barzilai says the 14th-century Haggadah was a wedding gift from his grandmother’s family to his grandfather, Ludwig Marum, a lawyer from the German town of Karlsruhe who served in Germany’s parliament and opposed Hitler.

The Nazis paraded Marum and other opponents across town before taking them away. Marum was later killed at the Kislau concentration camp.

A Jewish lawyer named Shimon Jeselsohn who worked with Marum managed to flee and eventually moved to Israel after World War II. One day, he read in the newspaper about a special Haggadah purchased by the Bezalel National Museum, the forerunner to the Israel Museum.

Jeselsohn recognized it as the Birds’ Head Haggadah. Marum had kept it in his law office, Jeselsohn said in his memoirs.

Curious as to how the manuscript ended up in Jerusalem, Jeselsohn began making inquiries. The museum director told him a Jewish immigrant from Karlsruhe brought it after the war. When Jeselsohn asked the immigrant where he got it, he said a Jewish doctor had given it to him. But when the doctor denied it, the immigrant offered no further explanation, and Jeselsohn grew suspicious.

He wrote to Barzilai’s aunt, Elisabeth, who had survived World War II and moved to New York, to update her about the Haggadah’s journey.

After a visit to Israel in 1984 to see the Haggadah at the Israel Museum with Barzilai, Elisabeth wrote to the museum that she believed the immigrant who had brought it to Jerusalem “had no right to sell it,” but that the Marum family wanted it to remain at the museum “for the benefit of the public.”

For years, the family did not act. Dominique Avery, Elisabeth’s daughter, says her late mother thought she had no recourse to retrieve the manuscript and she deferred to Barzilai.

After Barzilai heard a speech last year at the Israel Museum by E. Randol Schoenberg, the lawyer who retrieved the Klimt paintings, Barzilai enlisted the lawyer’s help.

The family’s demands are delicate, because they are leveled at the leading museum of a country that gave refuge to Holocaust survivors and that has long seen itself as a caretaker of the cultural artifacts of Holocaust victims.

“The Israel Museum should be even more sensitive to the claimant’s side,” said Schoenberg.

The museum said it has in recent years restituted 18 works looted during World War II, and is in the process of restituting three more works. There are two researchers dedicated to combing through the museum’s collection for looted objects, the museum said.

Why Barzilai waited until his 70s to pursue the manuscript is another question mark in the story. Barzilai spent his childhood with an adopted family, and only learned as a teenager that he had been adopted and that his biological parents had perished in the Holocaust.

It was too painful a truth to bear, he said, and he wanted to forget his connection to the Marum family. “We were two separate identities,” he said. Even when he accompanied his aunt Elisabeth to see the Haggadah, he said he took no special interest in the manuscript.

Through his quest to reclaim the Haggadah at this stage in his life, Barzilai says he has reclaimed a part of himself.

“The Haggadah,” Barzilai said, “was a trigger.”