A painting bought in Co Down for just £350 could be an American art treasure worth up to £10m.
Canadian art collector Blair Mooney is offering a $5,000 (£2,600) reward to anyone with information about the oil painting - believed to be by Edward Hopper - that will lead to its final authentication.
Hopper was a famous artist whose depictions of modern American life are part of popular culture, with many reproduced as posters.
Blair part-owns what is thought to be an early version of Hopper's High Noon piece - Study Of High Noon - after it was purchased on eBay from a Downpatrick businessman in 2007. Since then $50,000 has been spent trying to authenticate it.
"It is likely to have been originally bought at a flea market or car boot sale, so I am hoping someone will look at this painting and say something like: 'That used to be in my granny's attic'," he told the Down Recorder.
Toronto farmer Blair, who got into art dealing as his wife has a gallery, thought the signed Hopper was perhaps a tribute piece.
And he is more used to dealing in modest profits and not the millions the artwork is thought to be worth.
"When they bought it I was not sure it was authentic," he said.
"Some said it was a little rough. It looked like his work, but not his work. It was done roughly, it was a study."
An examination of Jo Hopper's diary appeared to confirm changes made to her husband's High Noon painting.
Then forensic testing in 2012 led Blair to believe a "life changing" amount of money could be on the cards.
Dr George Benn from Queen's University Kingston, Canada, was among the experts carrying out tests on the Downpatrick painting to compare it with the original, which is on display in Ohio's Dayton Art Institute.
"Our painting was X-rayed using infra red ultra violet light," Blair explained.
"As we started seeing what was underneath, Janice Passafum (a Toronto conservator) jumped up and started dancing.
"I heard: 'Congratulations, you have got yourself an American art treasure'.
"I had to take a little stroll."
Blair said if the painting does prove to be a genuine Hopper, it would be worth millions.
He said: "I will be financially secure for life.
"It has taken a lot of work since 2007 to get here and I have been here in Downpatrick over the past week trying to tie up the final ends, dot the Is and cross the Ts."
Blair has since returned to Canada.
If you can assist him please email firstname.lastname@example.org or call 00 151 9534 5785.
Edward Hopper was born in New York State in 1882 and died in 1967. He was a prominent realist painter and printmaker, most popularly known for his oil paintings. His spare and finely calculated renderings reflected his personal vision of modern American life. The best-known of Hopper's paintings is his 1942 work Nighthawks. It shows customers sitting at the counter of an all-night diner. and has become an iconic modern image.