The painting is expected to fetch up to £350,000
Art experts have decided that a JMW Turner painting long-thought to have been of Bass Rock in Scotland is in fact the Mew Stone off Plymouth Sound.
The painting is being sold at auction by Christie's on Wednesday and is expected to fetch up to £350,000.
The work has been sold twice before, each time labelled as a depiction of the Bass Rock in the Firth of Forth.
But experts have decided the distinct silhouette is that of the Mew Stone at the entrance to Plymouth Sound.
Turner is known to have travelled to the South West three times during his career, in 1811, 1813 and 1814.
During his visits he made a number of sketches which he continued to use late into his career.
The Mew Stone lies about a mile offshore in Wembury Bay
In August 1813 Turner sailed past the Mew Stone on a trip from Plymouth to Burgh Island in Bigbury Bay in the company of the journalist Cyrus Redding, who described the passage as "extremely rough with high seas running".
When they arrived at the island Turner made some pencil sketches.
The painting was first sold - as Bass Rock - to renowned art historian John Ruskin in 1869.
It was also called Bass Rock when it was bought in 1956 by the collector Denys Sutton - from whose collection the 7in x 10in (17.8cm x 26 cm) work is now being sold.
But closer examination of the artist's sketchbooks ahead of the sale have led art historians - including Turner expert Ian Warrell - to deduce it actually came from The Devonshire Rivers No. 3 and Wharfedale sketchbook dating from 1814-16.