Instead it is a rare, and historically important, rendition of England's biggest amusement park - Blackpool Pleasure Beach.
This new information emerged after David Graham, a Blackpool-based journalist, came across stories of the rediscovered work in the national press.
The accompanying image looked familiar: "I was taken quite by surprise when I saw it. A double-take and I realised that, yes, this was something very familiar: the same Blackpool pleasure beach that I drive past every day.
"Much as I didn't want to disappoint the residents of Beswick [near Manchester, where Sotheby's believed the scene was set], there was no way round it - this was Blackpool."
Mr Graham was quick to recognise the architectural outlines of fairground rides that have not changed in some three quarters of a century: the distinctive Noah's Ark attraction (one of only two left in the world); the tall, elegant Art Deco tower designed by Joseph Emberton at the start of the Grand National Ride, and Sir Hiram Maxim's Flying Machine - the world's oldest flying ride.
After careful consultation with representatives at the Blackpool Pleasure Beach, Mr Graham contacted Sotheby's with the news.
James Rawlin, head of Sotheby's 20th-century British art department, who clearly does not go to Blackpool for his holidays, described the positive identification of the scene as "a phenomenally important development".
"We think of Lowry as someone who captures the social history of his time and place, but this painting is also a vividly accurate historical document. Works of such topographical accuracy are extremely rare in Lowry's oeuvre, as indeed are depictions of Blackpool: so far we've been unable to trace any important depictions of the city."
A Fairground has remained in the same private hands since it was purchased around 1950. It is expected to fetch up to £1m.
