The passing was captured on film: the violin’s elegant outline, the figure on its flamed-maple back, the wear pattern of its varnish.

Japan’s ambassador to Germany, Hiroshi Oshima, was on hand to witness the transfer. Nejiko Suwa, 23, played her new gift on the spot.

The next day Goebbels, the Nazi propaganda minister, wrote in his diary: “I am offering the Japanese violinist Suwa a Stradivarius violin. Oshima, who attends the reception of this young girl who makes an extremely likable impression, is delighted about this gift.”

Ms. Suwa responded with gratitude. “I will continue to work hard not to disgrace this masterpiece,” she told the Japanese press.

The setting was Berlin; the gift an 18th-century instrument said to be from the hands of a master luthier whose works mark the apex of three centuries of violin making. The ceremony a chance to cement an alliance and to thank the violinist for playing for Germans wounded in World War II.

Much is documented — if little remembered — about Goebbels’s gift on Feb. 22, 1943. But the origins of the violin itself remain a mystery. Was it confiscated property, one of thousands of musical instruments plundered by the Nazis, or otherwise obtained under duress from those persecuted during the Nazi era?

When Ms. Suwa and her violin returned to Japan, the whispers followed. They have trailed the instrument for nearly 70 years.

“I feel sympathy for Nejiko Suwa, who is caught between the love for the famous instrument she brought back to her homeland and decency,” Kibihiko Tanaka, a Japanese law professor, said in a newspaper opinion article published in 1946.

“I would like to give her advice,” he continued. If the violin “had been taken from the owner by the Nazis as it has been reported, let decency as a human being overcome your love as an artist, shake off your tears, and make a firm decision to return this violin to the former owner on your own accord.”

Ms. Suwa, who died in March at 92, and her family have rarely spoken of her violin. She has denied in interviews that it was stolen and said it had been purchased by Goebbels’s ministry from a dealer in Silesia, a region with a history of shifting German, Polish, and Czech borders.

Much has been written about the Nazi plunder of fine art, but there have been few efforts to analyze their confiscation of musical treasures. Now researchers are beginning to focus on the issue, and at the University of California’s Institute of European Studies, in Berkeley, I am conducting a project on musical losses, file by file, name by name. The analysis of authenticity and the history of ownership and possession, the provenance, are essential to the mission.

Where is the violin listed in Viennese records as an “Antonius Stradivarius Cremonensis faciebat Anno 1722,” confiscated in 1939 from the noted art collector Oskar Bondy?

Or two violins that had belonged to the Austrian composer Johann Strauss II, seized from his Jewish stepdaughter.

Did Goebbels give away a stolen treasure, or has Ms. Suwa been unfairly trailed for decades by the taint of his legacy?

During the war musical manuscripts, printed music, books and instruments were confiscated, swept up as war trophies, lost or displaced under circumstances of crisis. A Nazi unit known as the Sonderstab Musik was among those tasked with such looting.

Evidence of seizures and opaque transactions during the Nazi era are scattered in a sea of archival records in the United States and Europe. From the ghetto in Lodz, Poland, where approximately 200,000 Jews were sent during the Holocaust, comes the account of a decree from the authorities that ordered the surrender of all musical instruments.

“Beethoven, Mozart, Chopin, Schumann, will fall silent in the ghetto forever,” a captive resident wrote in 1944. “The street will notice nothing, harsh life will go on; and to the torments of hunger and cold will be added the unappeased craving for music.”

Fragile and temperamental, violins are serviced on the repairman’s workbench, and find their way into the inventories of dealers and other sellers. Their histories are found in certifications of authenticity, appraisals, bills of sale, photographs, ledgers, letters and diaries.

To this day, though, the provenance for instruments that surface in salesrooms each year is often scant or nonexistent. Trade customs intended to protect legitimate privacy interests of owners nonetheless frustrate efforts to trace instruments that may have been illegally taken by the Third Reich. Owner’s names are often blotted out on privacy grounds and replaced with terms like “from the collection of a professional musician.”

Sophie Lillie, an art historian who has investigated art losses under the Nazis said the trail of rare violins has not been as closely watched because the market has not been struck by a singular event, like the seizure of a disputed painting by authorities.

“There has not yet been the same kind of shock event in the world of violin commerce to force the trade into action,” she said in an e-mail.“But ignoring the problem is a potential liability, both financially (for buyer and seller) and morally.”

For years Ms. Suwa and her family declined my requests for information about her instrument. In 2007 I received a gracious answer from her nephew.

“Unfortunately she does not want to talk about that period include that episode,” he wrote. “Please remind. She is 88 years old now and when she left Japan to Europe, she was only 16 years old.” He apologized for not saying more.

When we spoke by phone several weeks ago, the nephew said the violin was now his, but he said he could not discuss it further at this time.

Of course my interest is heightened because the instrument in question may be a Stradivarius. But is it?

The expert searching for authenticity looks for subtleties of identity. The wood selection may reveal geographic information specific to the maker. The character and quality of the varnish, its method of application, and the ground that penetrates the wood underneath may be indicative of authorship. The connoisseur considers workmanship, style, and idiosyncrasies, including tool marks, techniques of construction and mastery, or the lack of it. The maker’s design and execution of the f-holes cut into the shell-thin belly, or the carved nautiluslike scroll are just some of the hallmarks of a maker’s hand.

And then there is the label.

Violin makers have been placing labels inside violins for hundreds of years, just as others have been tampering with them to increase their value by adding, say, a famous name. Two days after Goebbels gave Ms. Suwa the alleged Stradivarius, a Japanese newspaper said the violin dates from 1722, a year that resulted, by some estimates, in 20 violins from Stradivari.

In 1722 Stradivari would have been 78 years old. Although no one is certain, experts speculate that he made roughly 1,100 instruments before his death in 1737. Far fewer are extant.

When Ms. Suwa received the violin, she was already a violinist on the rise. Born in 1920, she was a prodigy by 10 and studying with the Russian violinist Anna Bubnova-Ono, Yoko Ono’s aunt by marriage. In 1936 she left Japan for Brussels and moved to Paris in 1938 to work with Boris Kamensky. She had her debut in Paris on May 19, 1939, just a year before the Nazi invasion of France.

Ms. Suwa performed throughout Europe during the war. She was a featured soloist with the Berlin Philharmonic in October 1943, and two months later Goebbels wrote his second and last diary entry about her:

“At noon I am a guest with Oshima. The famous Japanese violinist Nejiko Suwa plays for us a concert by Grieg and some smaller bravura pieces, with a superb technique and a brilliant display of art. I had given this violinist recently a Stradivarius violin as a present. By the way she plays I noticed that the instrument is in good hands with her.”

As Nazi Germany’s propaganda minister, Goebbels controlled music policy through the Reich Chamber of Culture, and its music division, the Reichsmusikkammer. Employment was restricted to Aryan musicians. Composers like Mahler, Martinu and Mendelssohn were blacklisted on the basis of religion, politics and race.

Goebbels also equipped musicians with high-end instruments. In his diary on Dec. 17, 1940, he wrote of buying a number of master violins for use by German violinists. His ministry was also involved in this process, lending 18th-century Italian violins to expert players, including musicians in the Berlin Philharmonic. A May 5, 1942, government memo says, “The Ministry is in search of a genuine Stradivarius for the Concertmaster.”

Military records confirm the wartime transfer of musical instruments to German musicians, like the “1765 Guadagnini” that the United States Army removed from the violinist Otto Schärnack in 1948. Schärnack said Goebbels had lent it to him in May 1944, its “origin: unknown,” “acquired from occupied countries during the war.”

When the Allies liberated Paris in 1944, Ms. Suwa fled to Berlin, traveling by train with the singer Yoshiko Kurachi. Ms. Kurachi recalled that the train made several emergency stops because of Allied airstrikes, and the two women were forced to jump from the train to take cover under nearby trees, or under the train. But Ms. Suwa was never separated from Goebbels’s violin, even as she slept.

In Berlin Ms. Suwa rejoined the Japanese ambassador and in April 1945, when the Japanese diplomatic staff evacuated, she fled by train for the Austrian Alps, where she was captured by soldiers from the United States Seventh Army in May, according to records in the United States National Archives. Ms. Suwa told them that she was the personal secretary of Ambassador Oshima’s wife, Toyoko Oshima, and that she had been studying the violin in Europe.

Ms. Suwa was placed onboard the liner Santa Rosa, in Le Havre, France, bound for New York. She was at sea in August 1945 when America dropped two atomic bombs on Japan. Her ship arrived in New York and anchored off Staten Island on Aug. 11, 1945, a few days before Japan announced its surrender. Customs officials removed and inspected 492 pieces of baggage from the ship. Records show that daggers, knives, revolvers and a sword were taken into custody, but no violin.

The following day Ms. Suwa and others from the Japanese diplomatic corps were taken to the Bedford Springs Hotel, a luxury spot in the heart of the Allegheny Mountains in Pennsylvania that served as a detention center. Twenty rooms had been secretly wired with microphones by the State Department in anticipation of the arrival of the Japanese.

That fall Ms. Suwa and the other 183 internees at Bedford were sent home by the State Department. Before their departure there was a celebration concert on Nov. 11, 1945. Invitees included the internees, United States officials and the hotel staff. Ms. Suwa, the Japanese conductor and composer Viscount Hidemaro Konoye, and the tenor Minoru Uchimoto were among the interned performers. Encores lasted late into the night. She played Goebbels’s violin.

“The sound of the Stradivarius disappeared into the thickness of the forest of Bedford Springs,” according to the author Yusuke Fukada, who interviewed some who were there.

Ms. Suwa arrived home in Yokohama on Dec. 7; a reporter met her on the wharf. “Is that the famous violin made by Stradivarius?” he asked.

Yes, Ms. Suwa said, holding the violin case firmly to her chest, “I have risked my life to protect it.”

In 1951 she boldly returned to America to perform in a benefit concert at the Hollywood Bowl. The Los Angeles press praised her as the “first Japanese musical star to set foot on American soil since the signing of the peace treaty,” which after prolonged negotiations had been signed by 49 nations one week earlier.

The star-studded cast of performers included 200 musicians and stars of stage, screen, television and radio, including Benny Goodman, Lionel Barrymore and André Previn. Bob Hope presided as master of ceremonies.

On Goebbels’s violin, before an American audience, Ms. Suwa played a piece she had performed in Toyko when she was just 10, the Concerto in E minor by Mendelssohn, a composer whose works had been banned by the Nazis.

Carla Shapreau, a violin maker and lawyer, is on the adjunct faculty at Berkeley Law School and is a co-author of “Violin Fraud: Deception, Forgery, Theft, and Lawsuits in England and America,” Oxford University Press (1998).