THE HAGUE — A Dutch art expert revealed on Tuesday that he has discovered a previously unknown portrait by Rembrandt, which he bought 18 months ago at a London auction for around 130,000 pounds (US$175,000).

Dating from about 1634, Portrait of a Young Gentlemen is the first unknown painting by the Dutch master to turn up in more than four decades and is likely worth millions.

It was bought in late 2016 by Dutch art dealer and expert Jan Six at a Christie’s auction in London.

"He knew instantly when he looked at it that it was a Rembrandt," his spokeswoman Ronit Palache told AFP.

"He has a huge knowledge about Rembrandt, and has spent years and years researching him. So he was unbelievably excited and also afraid that everyone would see how excited he was."

The painting has now been authenticated by other art historians, including another leading Dutch expert on Rembrandt, Ernst van der Wetering, she added.

It is undated and unsigned. And nothing is known about the painting’s history and provenance other than that before being auctioned it had belonged to a British noble family for about six generations.

The compelling portrait, which shows a young man dressed in a black cloak with a distinctive white lace ruffle staring out of the painting, will go on display for a month at the Hermitage Museum in Amsterdam from Wednesday.

The lace collar closely resembles others by Rembrandt, such as in the portraits of newly married couple Marten Soolmans, and Oopjen Coppit bought in 2015 for 160 million euros by France and the Netherlands in a joint purchase from the wealthy Rothschild family.

Art dealer Six, who has also written a book about his discovery, intends to sell the newly-found painting after it has been on display in Amsterdam.

But his spokeswoman refused to be drawn on how much it could fetch at auction, merely saying: "It will be more than 130,000 pounds."

It is believed the painting is also part of a double portrait, but further investigation about the canvas’s history will be needed to solve the mystery, said Palache. — AFP