A painting, whose authenticity has been questioned for decades, had been verified as a Rembrandt following eight months of scientific analysis.
The 1635 self-portrait shows the Old Master wearing a black coat, feathered bonnet and a metal band around his neck from a suit of armour while looking out at the viewer.
Rembrandt specialist Horst Gerson had doubted the authenticity of the picture, saying in 1968 that areas of the painting were not accomplished enough to be the work of the Dutch master.
He claimed the portrait was likely to have been painted by one of Rembrandt's pupils.
However, another specialist, Professor Ernst van de Wetering, said he believed the painting was genuine leading to The National Trust, which owns the picture, sending it away for scientific analysis.
Several layers of aged and yellowed varnish were removed by experts at the Hamilton Kerr Institute (HKI) in Cambridgeshire, so the artist's signature could be analysed.
The inclusion of the artist's left hand in the original composition and alterations made to the shape of his hat were revealed through infra-red reflectography and X-ray photography.
The analysis also showed that the wood was from the poplar/willow family, which Rembrandt used for some of his paintings.
Rembrandt, who is considered to be one of the greatest painters in European art history, was 29-years-old when he painted the portrait in 1635.
He was living in Amsterdam at the time and his self-portraits were becoming increasingly popular as his fame and wealth grew.
Rembrandt is thought to have produced at least 40 self-portraits, with the National Trust painting thought to be worth around £30 million.