The painting had been hanging for several years in the woman's home in Compiegne, north of Paris, before an auction specialist made the discovery. The tablet has now been sold for SEK 258 million at auction in France.
Do you also have an undiscovered masterpiece at home? Magnus Bexhed, CEO of Uppsala Auction Chamber, give three tips on what you can do if you have a precious item at home.
See the clip above.