Sotheby’s will auction a Vincent van Gogh painting estimated at $180 million and a Paul Cézanne estimated at around $120 million in New York this fall, works not publicly seen for half a century, according to CNN.

The auction house expects the 12-lot sale of the Blaquier-Arrieta collection, which also includes works by Monet and Renoir, to raise $450 million or more in less than an hour. Sotheby’s is promoting the group as the “El Dorado” of private art collections.

“It’s one of the greatest remaining collections of Impressionist and Post-Impressionist art in private hands,” said Helena Newman, chairman of Sotheby’s Europe, who called it “a mini Musée d’Orsay.”

The collection belonged to the late Argentinian businessman Carlos Pedro Blaquier and art patron Nelly Arrieta de Blaquier, who amassed it in London during summer visits, buying directly from the Lefevre Gallery. Their children are selling the works following Nelly’s death in 2020 and Carlos’ in 2023.

Philip Hook, a former senior director at Sotheby’s, told journalists at a London press view on Wednesday that the collection’s contents were a “constant” mystery of his career because the family never lent the pictures to museums and was based in Argentina.

For the last decade of his life, Blaquier, president of a sugar mill and member of one of Argentina’s most powerful families, was investigated for crimes against humanity for allegedly detaining activists during the country’s 1976-83 military dictatorship. He denied the allegations, the BBC reported, and never stood trial, according to his obituary in La Nacion. A Sotheby’s spokesperson said he was never convicted and always maintained his innocence.

The Van Gogh, Chataignier en fleurs roses et blanches, was painted in the last two months of the artist’s life at Auvers-sur-Oise, after his release from the psychiatric facility in Saint-Rémy-de-Provence where he had voluntarily spent a year. Sotheby’s notes the “vigor” and “optimism” of the period.

“It’s an amazing, exuberant palette,” Newman said, adding that only a “handful” of works from the end of Van Gogh’s life remain outside museums.

The Cézanne, Arlequin, is one of four Harlequin paintings and the only one not held by a museum, according to Sotheby’s. It passed through dealers Ambroise Vollard, Paul Durand-Ruel and Paul Rosenberg and was exhibited at the Museum of Modern Art in New York, the Tate in London and the Art Institute of Chicago before the Blaquier family bought it in 1975.

If both paintings break their artists’ records, it would be the second such double in one night. Christie’s 2022 sale of the Paul Allen collection saw Van Gogh’s Verger avec cyprès fetch $117 million and Cézanne’s La Montagne Sainte-Victoire sell for $137.7 million, both painted in 1888.

The sale follows a series of mega-collector disposals that have supported the high end of the art market, including the collections of S.I. Newhouse, Paul Allen, Pauline Karpidas and Leonard A. Lauder, the last featuring a Klimt that sold for $236 million, the second-most expensive work ever sold at auction. Newman acknowledged the sales reflect a generational shift as collections formed from the 1960s to 1980s come to market.

Several of the 12 works, including Renoir’s En Canot (Jeune fille à la barque) from 1877 and Pissarro’s La Place du Théâtre-Français et l’avenue de l’Opéra, soleil d’après-midi en hiver from 1898, were unveiled in London on Wednesday. The Van Gogh is travelling to Hong Kong for display ahead of the November evening sale in New York.