The Rijksmuseum has further authenticated two tiny portraits by Rembrandt after a lengthy investigation, the museum has said. The paintings, now on show at the museum in Amsterdam, date from 1635 and are the smallest the artist ever painted.

The people portrayed are plumber Jan Willemz van der Pluym and his wife Jaapgen Caersdr., the museum’s experts confirmed.  They were related to the Van Rijn family through the marriage of the couple’s son Dominicus to Rembrandt’s cousin Cornelia Cornelisdr van Suytbroek.

The portraits have a virtually unbroken line of provenance, remaining in the family of the sitters until 1760, when they were sold at auction in Amsterdam after the death of their great-great grandson Marten ten Hove (1683-1759).

From there they passed to  the collection of Count Vincent Potocki (circa 1740-1825) in Warsaw, before briefly entering the collection of Baron d’Ivry in Paris in 1820 and then James Murray, 1st Baron Glenlyon (1782-1837), who put them up for sale at Christie’s on 18 June in 1824, lot 76, listed as: ‘Rembrandt – very spirited and finely coloured’, where they were acquired.

For the last two centuries they remained in the same private British collection until they were bought  at Christie’s by the Holterman family for a reported €13 million earlier this year.

Rembrandt, who was much in demand as a portraitist at the time, probably did the paintings as a favour to the couple, which, researchers said, explains the size and the quick brushstrokes.

Material analysis and comparisons with other works by Rembrandt confirmed the paintings are from his hand.

The portraits are now on long-term loan to the museum and can be seen from December 13.

“The Rijksmuseum has the largest number of Rembrandts. I have close ties to the museum and, after all the work the team has done on the portraits it is only right they should be there,” Henry Holterman said.

According to director Taco Dibbets the paintings “bring visitors closer to Rembrandts circle of relatives. It is wonderful the portraits were bought by the Holterman family and that they were entrusted to the museum for millions to enjoy.”