An anonymous painting bought at auction based on a ‘hunch’ identified as a Rubens two-in-one | art

Is he a bald old man with a bushy beard and a wine-addicted look? Or a friendly young woman with flowing locks and a crown of braids?

For Belgian art dealer Claes Müller, the answer to this question matters no more than the fact that this particular picture of the optical illusion of a duck-rabbit was painted by Peter Paul Rubens.

Three years ago, a former Brussels-based gallery owner managed to acquire not only two studies of the Flemish Baroque artist’s heads in one painting, paying a “reasonable price” of just under €100,000 in an online auction.

The auctioneer, described only by Müller as “a less well-known northern European auction house” for fear of encouraging too much future competition, advertised the work as an undated study on paper by an anonymous professor of the “Flemish School.”

In the recent past, studies by Robbins have sold for between £500,000 and £1 million or more.

“I wasn’t sure it was a Rubens painting, I knew it looked very Rubens-like, so it was still a gamble,” said Müller, who describes himself as a huge fan of the artist and diplomat born in 1577. “I have a library of books about him at home and I look through them most evenings,” he told the Guardian. “It’s kind of addictive.”

He felt more confident when the painting was delivered to his home. “It was very dirty, but the varnish protected the painting very well, and I could see that it was of very high quality.”

But it was not until the picture was studied for several months last year by art historian Ben van Beneden, the former director of the Rubens House, that Müller began to feel confident that he had acquired a true ancient master.

“I think that’s very likely,” Van Beneden said. “You have to be careful because you’re dealing with a painting that’s not made for the market but as working material. But the craftsmanship is amazing – it has a very lifelike quality.”

The old man figure in the study appears in many of Rubens’s most famous paintings. “It is ubiquitous and has many uses,” wrote the Belgian newspaper De Standaard, which published news of the painting’s discovery this week.

In The Raising of the Cross, a high altarpiece in Antwerp Cathedral, the old man is depicted as Saint Amandus. In the painting The Adoration of the Magi, which hangs in the Prado Museum in Madrid, he is King Melchior in red. In the tribute money, at the Legion of Honor Museum in San Francisco, he is the Pharisee peeking out from behind Jesus.

Inspired by Italian painters, Rubens collected a series of different facial features that he could use in larger paintings. He is known to have created a prototype to study the head of the old man, which has since been lost. “Müller may have already found the prototype,” Van Beneden said.

But the woman inside the old man’s beard was drawn first. Rather than trying to create an optical illusion, Rubens may have reused the paper of an earlier painting and painted on it, Müller said.

The painting hangs in Muller’s home and will be on display at the Brava Art Gallery in Brussels on January 25. Even as a monograph, it deserves as wide an audience as possible, the art dealer said. He expressed his hope that the museum would agree to take the painting on long-term loan.