The friends from Owen Sound, Ontario -- Ken Marshall, 64, Ron Flarity, 60, Blair Mooney, 55, and Helen Flarity, 57, widow of Ron's brother -- have spent more than $40,000 over the past six years attempting to authenticate the painting they bought on eBay U.K. for $585, The (Toronto) Globe and Mail reported Saturday.
Hopper was an American realist painter and printmaker famous primarily for his oil paintings, most notably "Nighthawks" and "Cape Cod Evening." He died in 1967.
The friends' 14-inch by 18-inch painting, which depicts two women and a dog outside a house, closely resembles the 1949 Hopper painting "High Noon."
The friends are almost "100 percent convinced it's a Hopper," Ron Flarity said.
The Globe and Mail said should the painting be authenticated as a Hopper work, it could be worth millions of dollars.
The friends have a 61-page art report from two Toronto conservators that summarizes forensic testing, which is now making the rounds through the art world. They seek, however, further cooperation of the pre-eminent Hopper expert, New York art historian Gail Levin, who they first contacted more than five years ago and has twice dismissed the report.
The seller from whom the friends bought the painting died in a car crash in 2011. The Northern Ireland man was affiliated with a company that reproduced paintings but he had claimed to have bought this one at a flea market.
"They've got an uphill battle, they really do," said Bruce Loch, proprietor of Thurston Royce Gallery in Allentown, Pa., a highly regarded seller of works by Hopper, adding that if Levin will not authenticate the painting if there's the slightest doubt it's a Hopper.