A forgotten masterpiece by Salford painter LS Lowry is being auctioned with a price tag of up to £500,000.
The painting of The Liver Building in Liverpool was bought by Vernon's Pools founder Vernon Sangster in 1963.
It has remained in the family and has been seen in public only once - when it was exhibited at Liverpool's Walker Art Gallery in 1973.
Now the Sangster family is to sell the painting and two others by Lowry at Christie's in London on 9 June.
The rediscovered work is estimated to fetch between £300,000 and £500,000.
All three Lowry paintings are from the collection of the late Robert Sangster, racehorse owner and son of Vernon Sangster.
The artist is famous for his paintings of Salford and Manchester, which makes the Liverpool work, painted in 1962, all the more unusual.
A Christie's spokesman said: "This rediscovered masterpiece is one of the finest works by the artist ever to come to auction.
"LS Lowry's style saw him portray the townscapes created by the Industrial Revolution, often showing skylines of smoking chimneys and streets teeming with people.
"These landscapes were often composite images created partly in his imagination, but The Liver Building, Liverpool, steps away from this trend and offers a faithful view across the Mersey to the distinctive skyline of its eastern shore."
The other Lowry paintings up for auction are A Quarrel (1935), which portrays a street fight, and Procession In South Wales, Whit Monday (1963), showing a group of people dressed in their Sunday best.
The works will be included in Christie's 20th Century British Art sale.
Lowry, who was born in Manchester in 1887 and died in 1976, is most famous for his industrial matchstick men scenes.