A painting once used as a dartboard by juvenile delinquents has been identified as depicting the house of the Old Master Peter Paul Rubens.

The discovery was made during a programme by the National Gallery to research paintings in Britain's public art collections.

The artwork, Courtyard at the Rubenshuis, attributed to the Dutch painter Anton Gunther Gheringh around 1645-75, was found in the store of Buckinghamshire County Museum.

It had been there for 20 years since being rescued from Denham Court, a stately home, which is now the centre of a golf course but was once a youth detention centre. The picture was riddled with holes by the young dart players but has since been restored.

Anne Cowe, one of the 25 researchers despatched to investigate 8,000 works in 200 regional museums, said: "The artist's technique isn't of any great standard. It's not a masterpiece. But clearly they have done a good job in reproducing Rubens's house." The Courtyard painting is to be examined by an expert from Rubens's house, now a museum, in Antwerp.

Art lovers say they are particularly interested as the painting clearly depicts frescos known to have been designed by Rubens himself.

Other works whose histories have been uncovered by the project include The Death of Cleopatra by Benedetto Gennari in the Victoria Art Gallery, Bath.

It was found to have been a tactical gift - or bribe - from Gennari to the 17th-century politician and womaniser Sir Francis Gwyn. The artist wanted help to secure a royal stipend.

A display of some of the finds is at the National Gallery until 10 February.