A painting by the Austrian artist Gustav Klimt, that was believed lost for 100 years, has been found in Vienna.
Portrait of Fraulein Lieser once belonged to a Jewish family in Austria and was last seen in public in 1925.
Its fate after that is unclear but the family of the current owners have had the painting since the 1960s.
The im Kinsky auction house estimates the painting's value at more than $54 million (£42 million).
It called the rediscovery "a sensation".
"A painting of such rarity, artistic significance and value has not been available on the art market in Central Europe for decades," im Kinsky said in a statement.
The portrait will now be put up for auction on 24 April on behalf of the owners, and the legal successors of the Lieser family.
This is based on the Washington Principles, an international agreement to return Nazi-looted art to the descendants of the people they were taken from.
Before the auction, the painting will be presented at various international locations including the UK, Switzerland, Germany and Hong Kong, the auction house said.
The portrait once belonged to the Lieser family, who were wealthy Jewish industrialists in Vienna.
Ernst Ploil, co-Managing Director of Kinsky Auction House, said they had so far found no evidence that the work had been looted or stolen before or during World War Two.
"The painting is described as lost in all catalogues raisonnés (comprehensive lists of Klimt's work). In our circles, 'lost' means probably destroyed, probably burnt during the war, but in any case no longer in existence; it was not to be expected that it would ever reappear.
"We took an active approach and not only researched the Lieser family as potential restitution claimants, but we also approached potential representatives based on our experience from previous restitution proceedings."
Klimt's art has fetched huge sums at auction in the past.
His Lady with a Fan piece sold for £85.3 million in June, making it the most valuable work of art ever sold at auction in Europe.
