A man was shocked after picking up a sketch at an estate sale for £22 ($30) as he later learned it was actually an original artwork worth around £37m.

The man, who wishes to remain anonymous, liked the unframed sketch of a mother and child, which was elegantly drawn onto yellow linen.

He didn’t suspect it was an original piece of artwork of any significance, even though it had one of the art world’s most well-known monograms— Albrecht Dürer ‘s “A.D.”, as the Smithsonian Magazine reports.

Now the artwork has been assessed by experts and scholars, who agree the sketch is an original – and conservative estimates put the value at around £37m ($50m).

The Albrecht Dürer sketch

The sketch was sold in Massachusetts in 2016 by the family of late architect Jean-Paul Carlhian, and previously it had been passed down by the family.

Clifford Schorer, an art collector, said: “It was an incredible moment when I saw the Dürer. It was either the greatest forgery I have ever seen – or a masterpiece.”

The artwork was verified by two telltale features, the artist’s monogram was done with the same ink featured in the drawing, and it was done on paper bearing a watermark seen on more than 200 sheets used by the artist.

Albrecht Dürer is a German painter from the renaissance movement, who established his reputation and influence across Europe in his twenties due to his high-quality woodcut prints.

He was in contact with the major Italian artists of his time, including Raphael, Giovanni Bellini, and Leonardo da Vinci, and from 1512 was patronized by Emperor Maximilian I.

Meanwhile, an amazed pensioner has found that a piece of jewellery she was about to bin during a clearout is in fact a diamond worth £2 million.