(Amsterdam) Priceless family treasures: Christie’s has discovered two portraits painted by Rembrandt, hidden from view in a private collection for 200 years.

A British family “pretty casually” enjoyed these oil paintings by the 17th-century Dutch master, until an expert at the prestigious auction house spotted them during a routine appraisal.

The works, the last pair of Rembrandt portraits to remain in private hands, are expected to fetch £5-8 million (£8.4-13.4 million) when auctioned at Christie’s in London on July 6.

“I first encountered these paintings a few years ago during a routine appraisal and was stopped dead in my tracks,” said Henry Pettifer, Old Master Paintings Manager at Christie’s.

“I was truly stunned to discover that the images had never really been researched and discussed in Rembrandt literature for 200 years,” he told AFP. while the portraits were exhibited in Amsterdam.

The 20 cm high oval portraits, believed to date from 1635, depict an elderly plumber called Jan Willemsz van der Pluym and his wife Jaapgen Carels.

The couple, painted in an intimate style unusual for the artist, were among Rembrandt’s family friends and hailed from his hometown of Leiden.

An ancestor of the current owners bought the paintings at auction at Christie’s in 1824, where they were listed as Rembrandt. Since then, they have remained in the same collection.

“They have stood quietly, loved by the owner’s family for two centuries…much appreciated, rather casually,” Pettifer said.

After they were spotted, work began to verify that they were authentic Rembrandts.

“The images were unknown, initially had to be treated with great caution,” the official stressed.

Christie’s has called on art experts, including the Rijksmuseum in Amsterdam, which has one of the largest Rembrandt collections in the world.

The museum’s scientific team examined the works for nearly two years, Christie’s expert Manja Rottink told AFP.

Specialists have verified the lineage of ownership of the paintings, which are mentioned in an inventory of the eldest daughter of the paintings’ subjects, the house’s international specialist in Old Master paintings said.

They also checked Rembrandt’s signatures, including whether they were done at the time with liquid paint, and compared the artistic style to other works by the artist.

“The conclusion was that indeed they are by the artist […] it is quite extraordinary,” she said.

The paintings also shed new light on the style of Rembrandt, best known for his much larger portraits commissioned by wealthy Dutch families.

“It’s something slightly different, something much more intimate…more personal,” Pettifer said.

The rediscovered Rembrandts are now on tour in New York and London, before being auctioned off in London next month.

It is unclear whether the buyer will be an individual or a museum, but one thing about the sale is certain.

“They’ve been whole their whole lives, so we’re selling them together,” Pettifer said.