When a stranger calls up a museum and offers to donate a 19th-century painting, it may or may not be good news. Remember the story last fall of the mysterious forger who tried to donate imitations of American Impressionist and other works to over 30 different U.S. institutions? But when Cologne's Wallraf-Richartz Museum was contacted by an elderly woman offering to donate a Monet painting, the museum's curator of 18th- and 19th-century painting and sculpture, Götz Czymmek, was thrilled to discover it looked like the real thing.

There was just one catch: The woman, who remained anonymous, didn't want the painting exhibited during her lifetime, Deutsche Welle reports. She gave the work to the museum 20 years ago, with instructions to store it in the basement until her death. And so, between 1991 and 2010, she sent Czymmek a letter at least once a year, with a brief message: "I'm still alive!"

She recently passed away, which means that Czymmek is now free to reveal the story and exhibit the painting.

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When he arrived at the donor's house, he found the painting in a box in
the middle of her living room. It immediately struck him as rare and valuable — a surprise, since paintings are often donated to museums when they are unsellable or in
very poor condition, he said. The donor insisted that he take it with him
immediately. "And so, I drove back to Cologne with a Monet in a
cardboard box in the back seat of my car," Czymmek told Deutsche Welle.
The work, "Spring Mood in Vetheuil," was painted in 1880 and depicts the town where the artist lived from 1879 to 1881.

The Wallraf-Richartz Museum now has six Monets — though at one time it would have added them up to seven. In 2008, the museum discovered that "The Seine at Port Villez," which had been donated in 1954, was a fake. But Czymmek said that he is sure that this new, long-anticipated Monet painting is the real thing, as evidenced by a sticker on the back from the Berheim Jeune Gallery in Paris, which is known to have dealt in Monet's work.

Yet one sticky issue could remain regarding the painting's provenance: The owner acquired it in the 1940s, a time when the Nazi regime seized works from many Jewish dealers and collectors or pressured them into selling them. Czymmek said that he "cannot exclude" the possibility that the painting was acquired through illegitimate means, but that "the painting has been available for a few months now, and so far no one has claimed it."