One of only two paintings by Johannes Vermeer that remains privately owned is going under the hammer at Christie’s, the Guardian reports. The authenticity of the piece, which depicts Saint Praxedis, has long been disputed.

However, new research led by the Rijksmuseum in Amsterdam recently proved that the oil painting is indeed by the 17th century Dutch master, making it his earliest surviving work. Some of its white lead paint precisely matches another paint found in an undisputed work by the artist, Diana and Her Companions.

Saint Praxedis (c. 1655) belonged to Barbara Piasecka, who died last year. The American collector also once owned a Rembrandt, which sold at Christie’s for over £20 million four years ago.

The rarity of the Vermeer is sure to provoke much excitement. The only other privately held example of the artist’s work sold at Sotheby’s in 2004 for over £16 million.