A 17th Century portrait by Spanish painter Diego Velazquez is back on show at New York's Metropolitan Museum of Art years after it was wrongly identified as not being a genuine work.
The Met downgraded the painting of King Philip IV in 1973, determining it was likely done by an assistant or follower studying under the artist.
But experts reversed the decision after a year's worth of restoration.
The portrait can now be seen in the European Paintings galleries.
It is one of only just over 100 known works by Velazquez, who was the king's leading court artist and painted him throughout his reign.
The painting, which had been on display since 1914, had not been cleaned and restored since 1911 and scholars debated for years whether it was genuine.
It was among 300 disputed works all downgraded by the Met 37 years ago, despite the museum owning the artist's signed receipt of payment from the king.
But the painting of the 18-year-old king underwent a complete restoration a year ago to remove layers of repainting and thick varnish.
X-rays were also used to look though to the original paint, which revealed the distinctive brush strokes of Velazquez.
"The picture was quite honestly a bit disappointing in the state in which it was shown," Keith Christiansen, the Met's chairman of European paintings, told the New York Times.
"For many years, scholars that I have had conversations with in front of the picture have said, 'the only way we will ever be able to decide what involvement Velazquez had in this picture is if you clean it'."