The following year, the provenance said, Carol I bequeathed the work to the institution of the Romanian Crown, which received the painting after the king’s death in 1914 and held on to it until 1947. That year, according to the provenance, the Romanian government allowed possession of the painting to transfer to Michael, who had ascended to the throne at the age of 18 amid the chaos of World War II.

Michael altered history in 1944, at 22, when he arrested Ion Antonescu, the fascist dictator of Romania and an ally of Hitler’s. Antonescu was then locked in a vault where Michael’s father, King Carol II, who was forced into abdication by General Antonescu in 1940, had once kept the royal stamp collection.

Soon afterward, Michael renounced Romania’s connection to the Axis powers and turned Romanian divisions against the Nazis, inflicting severe losses. Some historians believe that those actions helped shorten the war and saved tens of thousands of lives.

By 1947, however, Communists tied to Stalin controlled Romania. Michael said the country’s prime minister, Petru Groza, threatened to execute 1,000 imprisoned students if he did not give up the throne.

On Dec. 30, 1947, Michael left Romania via train with more than 30 family members and friends, issuing a decree that said the monarchy was an obstacle to the country’s future. While in exile, Michael and his wife, Princess Anne of Bourbon-Parma, lived mainly in Geneva.

The Romanian government eventually came to believe that six weeks before he abdicated, Michael removed 40 paintings from the country on a trip on the Orient Express to attend the wedding in Britain of his cousin Philip to Princess Elizabeth, the future queen. He deposited some at a Swiss bank and left others in Florence, the lawyers for the government maintained.