The 10x8ins black and white photograph, simply titled 'Sheffield', was taken in 1937 and is valuable because it is by one of Britain's greatest photographers, Bill Brandt.
It shows a toddler in a Sheffield back yard, with clothes on a washing line in the background.
The only mystery is the identity of the toddler, who would now be in her 70s, but who was never named.
Bill Brandt's photographs are now much sought-after and sometimes sell for extraordinary sums. One of his views of London, taken in 1952, was sold at Christie's in Paris last year for a staggering £53,608,a new world record for a Brandt photograph. The Sheffield picture will be auctioned at Sotheby's in London on November 14.
Brandt's fans include the Yorkshire-born artist, David Hockney, who says: "Bill Brandt made pictures of the north of England around the time I was born.
"They are carefully composed and seem to me very real. I say he made pictures, rather than took them, because he regarded the image as the important thing, rather than the purity of execution.
"His techniques understands the power of images. It's that, for me, that gives them their strength in a time when a photograph as documentary evidence is fading fast. They survive and enter the memory because they were constructed by an artist."
In their book, 'Brandt: The Photography of Bill Brandt', authors Bill Jay and Nigel Warburton say: "During the 1930s and 1940s, Brandt was at the centre of the thriving photojournalistic industry, doing a series of important stories for photographic magazines such as Liliput and Picture Post.
"Among these was the series on the industrial cities and coalmining districts of northern England, which revealed the desperation of England's industrial workers at the time."
Bill Brandt was born Hermann Wilhelm Brandt in Hamburg, Germany, in 1904 and died in London in 1983 aged 79.
According to the Dictionary of National Biography "Bill Brandt - Billy to his closest friends - was tall, fair-haired, slim and handsome, with a beautiful smile and a surprisingly hearty laugh.
"He always kept a slight accent. But in later life he refused to admit to being German or even to speaking the language. He was ultra-sensitive, private and shy and suffered from diabetes. Despite his apparent frailty Brandt was - for many - the most vigorous, compelling and poetic photographer working in Britain in modern times."

WERE you the toddler in Bill Brandt's Sheffield photograph? Do you know who she could be, or where exactly the photograph was taken? Email starnews@sheffieldnewspapers.co.uk or call the newsdesk on 0114 276 7676.