The Cologne Museum claims that a little old lady contacted the museum with a lost Monet and donated it upon the condition it would not be displayed until after her death. Twenty years later, the work is now in a show:

“Spring mood in Vetheuil” […] has been identified as an original dating to 1880 and depicting a scene from the town where Monet lived from 1879 to 1881.

[…] 1880 was a crucial year for Monet, as it laid the foundation for his landscape painting until well into the 20th century. But the painting itself does not fill in any gaps in Monet’s body of work, contended . Mario von Lüttichau, curator for 19th and 20th century collections at the Museum Folkwang in Essen.

“Of course, it’s always significant to uncover a painting by a major artist like Monet,” he told Deutsche Welle. “But this landscape is not an especially pivotal work, and art historians hadn’t been on the look-out for it.”

Previously unviewed Monet painting on show in Cologne museum (Deutsche Welle)