Seven-year-old Anthony Thériault said he’s collected hundreds of rocks playing on the Restigouche River near Campbellton, N.B.
Then, last week, he stumbled on a novel find.
"I saw something shiny, and that was the bottom of the ring," he said in French.
Anthony then brought it home for his dad to investigate.
"All of a sudden, he said 'Look, Dad, what I found at the river,' " Shawn Thériault said.
"I looked at it, this Stanley Cup ring that said 'Elmer Lach' on it, and then I started checking on it."
Former Montreal Canadien Elmer Lach helped lead the Habs to Stanley Cup victory three times in his career in the 1940s and '50s.
The Thériaults say they've been Habs fans for years.
They say they don't know for sure whether the ring is real, but they have a theory that Elmer Lach may have lost the ring while fishing there.
For years, the Restigouche River has been a favourite fishing hole for Canadian celebrities, including Elmer Lach's linemate, Maurice (the Rocket) Richard.
Together with fellow Canadien Toe Blake, the three made up the team's famous "Punch Line" that helped the Canadiens win the Stanley Cup in 1944 and 1946.
If the ring is real, it represents Elmer Lach's part in that 1946 victory over the Boston Bruins.
One year before that, Lach received the NHL's Hart Trophy, distinguishing him as league MVP.
Shawn Thériault and his wife, Geneviève, have been calling jewellers to determine whether the ring is authentic.
"If it's real, we're either going to have to try to contact the family or the Montreal franchise to try to see what we can do with it," Shawn Thériault said.
They plan to investigate further when they visit Montreal next month.