The 1843 image of John Quincy Adams is now set to sell for £200,000
The earliest-known surviving photograph of a US President is expected to sell for almost £200,000 after it resurfaced for the first time in almost 175 years.
John Quincy Adams was the sixth President of the US, holding the position from 1825 until 1829.
And in March 1843, as a 76-year-old member of congress, he sat in a Washington portrait studio to have his picture taken by Philip Haas.
The detailed portrait shows the elderly statesman, complete with facial hair, sitting on a wooden chair with his legs crossed, revealing his light-coloured socks.
It is known as a daguerreotype, the first commercially successful photographic process, which takes its name from its inventor, the Frenchman Louis Daguerre.
Photography was in its infancy at the time, with Daguerre capturing a human on camera for the first time in Paris in 1838.
The Adams image was produced on a silver-coated copper plate rather than on photographic papers, so is unique as there are no negatives.
Adams, who died in 1848, gave the daguerreotype to fellow representative Horace Everett and it has remained with the family ever since.
Over the years, its importance was forgotten until, in the 1990s, it was discovered by Everett's great-great-grandson who was going through his late parents' possessions.
He assumed it was a relative and only recently discovered the photo was of one of the first presidents of the US.
Sotheby's has now announced it will be auctioning the photograph on October 5 in New York - and has given it a guide price of $150,000 to $250,000 (£115,000 - £195,000).
Emily Bierman, head of Sotheby's photographs department, said: "As the sixth President of the United States, John Quincy Adams is believed to be the 'earliest' US President to have been photographed.
"Although out of office for 14 years by the time that this photograph was made, the 75-year-old was still serving his country in the House of Representatives as congressman from Massachusetts.
"This photograph provides a rare, fascinating glimpse into the later life of one of our earliest presidents.
"The interest in this portrait will likely be broad, from school children studying American presidents to serious collectors of historical objects and rare photographs"
On the rear of the photograph it says, in handwriting J.Q. Adams, Hon Horace Everett, Windsor, Vermont.
There is also a bookplate which says it was 'Presented by J.Q.A. to his Kinsman H.E. 1843.
This is accompanied by the Everett family crest and the acknowledgement it is one of the earliest daguerreotypes
Ms Bierman believes it is one of the most important historical photos to be offered publicly in more than 20 years.
She added: "With a piece as early and as special as this, comparisons are few and far between.
"A terrific daguerreotype of (vice president) John C. Calhoun from 1849 came to auction in 2011.
"Going much further back - to 1996 - two daguerreotypes of Frederick Douglas (circa 1852) and John Brown (1847) were offered, each selling for over $100,000.
"While Adams is known to have sat for a number of photographers in the last decade of his life, exceedingly few of these daguerreotypes are today known."
The $150,000-$250,000 estimate for the Adams photograph may turn out to be a modest guide.
When Sotheby's auctioned the daguerreotype of Calhoun in 2011, they gave it an estimate of $50,000 but ended up selling for $338,500.