LONDON.- The long, thin piece of metal looked like a scaffolding pole when Trevor Penny saw it on the banks of an English river in November.

That would not have surprised Penny, who, while practicing his magnet fishing hobby, has unearthed household items, tools and other metal debris from the waterways near his Oxfordshire home. (Magnet fishing is pretty much what it sounds like: A strong magnet is attached to a rope, which is then tossed into a body of water.)

But his find that day was much more dramatic: a rusty Viking sword that had been there for more than 1,000 years.

The sword, found in the River Cherwell and identified by an archaeological group that tracks public finds, most likely dates to a period between A.D. 850 and A.D. 975. Penny said he handed it over to the Oxfordshire Museums Service this week, where it is expected to be put on display after restoration.

The discovery evokes a medieval era during which Vikings landed in the British Isles, raiding, plundering and trading their way through England and Scotland. Their incursions did not last, but their descendants still make up part of the British population today.

In recent years, metal detectorists have helped unearth artifacts and treasure that had lain buried underground for centuries.

Detectorists in 2007 found a hoard of Viking treasure near North Yorkshire that experts called one of the most significant finds in Britain. Another hoard buried during that era was discovered in 2014 in Galloway, Scotland. But not everyone who stumbles across such discoveries has been immediately transparent: Two men in 2019 were convicted of theft and ordered to pay $1.5 million after they concealed the discovery of an Anglo-Saxon hoard of treasure and sold some of the items.

When Penny, 52, realized what he had found, he contacted a local official responsible for identifying the public’s archaeological finds.

The discovery was “one further puzzle piece that can cast light on our shared heritage,” said that official, Edward Caswell, who documents Oxfordshire finds for the Portable Antiquities Scheme run by the British Museum. More analysis was needed, he cautioned, but experts confirmed that the sword fit with others from that era.

“We do find Viking weapons, including swords, deposited in rivers in England,” said Jane Kershaw, an associate professor of archaeology at the University of Oxford. About 70 such swords have been found in Britain, she said, and while Penny’s sword might have been dropped by accident, they were also often intentionally thrown in waterways as part of a ritual.

“Rivers were seen as gateways to other worlds, where gods and other creatures or spirits might live,” she said, adding that archaeologists interpreted such rituals as a Viking plea for protection or luck, perhaps in battle.

Many such weapons have been found in the north and east of the country, Kershaw said. She called the sword a “rare example” of Viking activity in the area.

“It is outside the normal find zone for these weapons,” she said. “But the Vikings, they were active in that area. There is a lot that we don’t know about their activities.”

Hobbyists are increasingly making important discoveries, and Kershaw said it was critical that they report their finds. “It’s hugely valuable information,” she said. “As long as they are recording it, this is having archaeology that otherwise would be lost.”

But who owns artifacts that are found today can be a thorny issue, and can depend on whether they are classified as “treasure.”

According to the Treasure Act in Britain, metal objects more than 300 years old when found must be reported to authorities within two weeks. Museums have the chance to claim objects, and finders and landowners may receive a reward, after an object is valued if it is deemed to be a treasure.

Penny found the sword on land owned by the Canal & River Trust, a charity that manages many of England’s inland waterways. The group has banned magnet fishing on its property, saying that it can be “dangerous” and that sharp objects could cause problems for visitors.

But the charity called the sword an “exciting find,” and it has agreed with Penny to transfer any potential ownership rights over the sword to a local museum.

Since he began magnet fishing three years ago, Penny has helped dredge up other discoveries, including old railway tools and a grenade suspected to be from World War II that had to be safely detonated by authorities.

“It’s a great way to meet people,” said Penny, who often brings the metal he collects to a local scrapyard. “We get to talk to lots of people passing, who all thank us for cleaning the environment.”

He posts about his finds to a local magnet fishing group, and so far has no plans to stop.

“I will keep fishing,” Penny said. “Hopefully with permission to do so.”

This article originally appeared in The New York Times.