A small marble sculpture thought to be a copy of the French artist Auguste Rodin’s work has turned out to be the real thing, selling for almost $1m at an auction in France on Monday.

The sculpture, called “Despair”, a figure of a woman hugging her knees and holding one foot, is a work by the famed sculptor from 1892 that had disappeared after being sold at an auction in 1906.

For the owners, “Despair” turned to delight when the piece they believed to be a Rodin copy was confirmed as authentic by the Comite Rodin after a six-week probe.

French auctioneer Aymeric Rouillac described it as an “extremely rare” find and the work was put up for auction and eventually sold for €860,000 (£725,000; $982,000).

“Despair” was originally modelled by Rodin as part of his series of figures for The Gates of Hell.

According to the Musée Rodin, the figure is a depiction of sorrow and the French sculptor created other versions after it was positively received.

After the family who owned the 28.5cm (11 inches) marble figure – which had sat on their piano for years – approached Mr Rouillac, he and his team spent months investigating the origins of the piece.

In March, Mr Rouillac brought the piece to the Comité Rodin, a research group dedicated to studying the works of Rodin, who confirmed its authenticity six weeks later.

The committee found that “Despair” had disappeared after being sold at an auction in 1906.

“We have rediscovered it,” Mr Rouillac told the AFP news agency.