Glass negatives bought for just $45 (£34) have been proven to be the work of iconic photographer Ansel Adams and are now worth $200m, it is claimed.
Painter and collector Rick Norsigian says he bought 65 negatives in 2000.
After years of trying to prove their origin, his lawyer now says experts have concluded "beyond reasonable doubt" that they were Adams' work.
The family of the landscape photographer, who died in 1984, have called the matter "unfortunate fraud".
Mr Norsigian said he spent years trying to verify the photos, which were believed to have been destroyed in a 1937 fire at Adams' studio in Yosemite National Park.
In the years after 1937 Ansel Adams became one of the world's best-known photographers, with original prints of his images of the American West, including Yosemite, selling for huge sums.
His images were produced with darkroom techniques that emphasised shadows and contrasts in his black-and-white images.
Defending his client's intentions, Mr Norsigian's lawyer, Arnold Peter, said the authentication involved experts in photography, handwriting and even meteorology - deployed in an effort to verify the weather conditions in Adams' famous landscape pictures.
Mr Norsigian released the finding on his website and at a press conference in Los Angeles on Tuesday. But some are still not convinced.
"It's very distressing," said Bill Turnage, managing director of Ansel Adams Publishing Rights Trust.
Mr Turnage says he is currently consulting lawyers about the possibility of suing Mr Norsigian for using Ansel Adams' name for commercial use, which is copyrighted under law.
Matthew Adams, the grandson of Ansel Adams, also admits he is "sceptical".
"There is no real hard evidence," he said.
Mr Norsigian purchased the negatives from a man who said he bought them from a salvage warehouse in Los Angeles, California in the 1940s.
Mr Norsigian has already created a website, from where he hopes to sell prints made from 17 of the negatives at prices ranging from $45 for a poster to $7,500 for a darkroom print.
A documentary on Mr Norsigian's attempts to have the negatives authenticated is also in the works along with a touring exhibition, which will debut at Fresno State University in California later this year.