A long-lost portrait by Gustav Klimt of a young woman sold for 30 million euros ($34.5 million) at auction in Vienna, Austria, on Wednesday. The Austrian modernist artist began work on the "Portrait of Fräulein Lieser" in 1917, a year before his death, and it is one of his last works, according to the Associated Press (AP). Bidding for the painting started at 28 million euros, and the sale price — which had been estimated to fetch 50 million euros or more — was at the lower end of expectations. It sold for 30 million euros to an unidentified buyer. The auction house Im Kinsky said "a painting of such rarity, art historical significance and value has not been available on the Central European art market for decades," according to the AP. Klimt left the painting, which has some unfinished sections, in his studio when he died of a stroke in early 1918, and it was later given to his family, the auction house said. Art historians Thomas Natter and Alfred Weidinger say the painting depicts Margarethe Constance Lieser, the daughter of Adolf Lieser. However, the auction house said the painting could also depict one of Justus Lieser's two daughters or his wife, Henriette. The painting's whereabouts after 1925 are "unknown," the auction house said. "What is known is that it was acquired by a legal predecessor of the consignor in the 1960s and then came into the possession of the present consignor through three consecutive inheritances," it said. The current owners were not publicly identified. The painting is being sold on behalf of those owners and the legal successors of Adolf and Henriette Lieser, under the Washington Principles — an international agreement to return Nazi-looted art to the descendants of those from whom it was taken. Read more: Quadro 'perdido' de Gustav Klimt durante 100 anos aparece e vai a leilão (Portuguese version)