For the longest time, "Portrait of Prince William Nii Nortey Dowuona" was thought to have been lost. Though Gustav Klimt portrayed the nobleman in 1897, the painting had not been seen since 1938.

The painting's recent reappearance caused an art world sensation and it is now on offer for €15 million ($16.3 million) at the TEFAF art fair in Maastricht, the Netherlands.

A collector couple brought the heavily soiled painting to the gallery of the Viennese art dealers Wienerroither & Kohlbacher, who specialize in Klimt's works.

"It was a huge surprise for us," Alois Wienerroither, managing director of the gallery, told DW.

Even though they have more than 25 years of Klimt expertise, the gallery owners did not immediately recognize the treasure hidden beneath the grime.

"We looked at the painting, it was dirty and also had a bad frame, it didn't look like Klimt at all," said Wienerroither.

After cleaning it, however, there was no doubt that it was Klimt's lost painting of a West African prince from what is now Ghana.

Gustav Klimt: a pioneer of the Austrian avant-garde

The Viennese artist Gustav Klimt (1862-1918) was one of Austria's most important painters in the late 19th century.

He is considered a representative of Viennese art nouveau and his abstract portraits of women, such as "The Kiss" and "The Golden Woman," are particularly famous.

In 1897, Klimt founded the so-called "Vienna Secession" with a group of 50 like-minded avant-garde artists who wanted to break with the realistic style of history painting, turning to a new art, art nouveau, instead. Klimt was the president of the new association.

It was during a period of transition that Klimt painted the portrait of the West African prince — depicting him with realism yet offering hints of what would come in later works.

For Wienerroither, the rediscovered work is a key painting in Klimt's oeuvre. "The floral background of the painting is already modern and is also reminiscent of the portrait of Sonja Knips, daughter of an officer's family, which he painted a year later, also with a floral background."

International ethnographic exhibitions in Vienna

The most up-to-date art historical research suggests the prince posed for Klimt as part of one of Vienna's so-called Völkerschau ethnographic exhibitions.

Though widely seen as racist and undignified spectacles from today's perspective, such "human zoos" were popular at the turn of the century.

The exhibitions took place across Europe, including in Germany, and saw people representing various ethnic groups kept in open spaces, like animals in a zoo, presented for public gawking under adverse conditions.

How did Klimt and the prince meet?

It had long been unclear how Klimt actually met the West African prince but in 2007, art historian, photographer and museum manager Alfred Weidinger published a catalogue of Klimt's paintings that documented the fact that the director of the Vienna Zoo had invited representatives of the West African Osu tribe to visit Austria in 1897.

The nephew of the Osu king, Prince William Nii Nortey Dowuona, was sent to Vienna as leader of the group.

The prince not only sat for Klimt, he was also depicted by artist Franz Matsch, whose painting of Nii Nortey Dowuona hangs in the Musee National d'Histoire et d'Art in Luxembourg.

Thrilling drama unfolds around prince's painting

After Klimt's death in 1918, Ernestine Klein bought the artist's studio and converted it into a villa. She may also have bought the portrait at a 1923 Vienna auction, though there is no documentation of such a sale. Nevertheless, there is a black-and-white image of the painting in the corresponding auction catalog.

In 1928, 10 years after Klimt's death, the painting appeared again, this time at a Klimt retrospective.

"And that's when we were able to find the return receipt," said Wienerroither, who had set out to trace the provenance of the painting, told DW. "Ernestine Klein got the painting back from the exhibition and signed for it."

However, as her husband was Jewish, the family had to flee from the National Socialists in 1938 when Adolf Hitler and the Nazis annexed Austria. "There is every indication that they left all their belongings behind in the house. When they came back after the war, everything was gone," said Wienerroither.

As the painting never appeared at auction after the war, the gallery owner suspects it changed hands through private art dealers.

When paintings confiscated or stolen by the National Socialists, for example, come up for sale, their origin and provenance must be checked. Wienerroither therefore visited Klein's descendants, with whom he reached a financial agreement.

"There are several heirs and it took a long time until we finally negotiated an agreement," he said.

Visit to the prince's family 

And yet, the story doesn't end here either. In Ghana, it is just the beginning. "It's been proven who this prince is, and the descendants have even been traced," said Wienerroither.

Again, it was a mere coincidence.

"Alfred Weidinger, who wrote the Klimt catalog, had been taking photos of kings in Africa for years," said Wienerroither. This is how he tracked down the family of William Nii Nortey Dowuona in Ghana.

"He is now in contact with the family. It's unbelievable. Apparently, they still have items they brought back from Vienna, they're still in the family," said Wienerroither.

Meanwhile, a meeting has been planned with Weidinger and William Nii Nortey Dowuona's descendants in Ghana. The story of Klimt, the West African prince and the journey of the painting that sprung from that meeting will be the subject of an upcoming 50-minute television documentary.

This article was originally written in German.