The artifact resembles a small buckle, researchers from the University of Colorado Boulder said in an announcement. How it got to Alaska remains a mystery.
"The object appears to be older than the house we were excavating by at least a few hundred years," research assistant John Hoffecker said in the release. Hoffecker led excavating at Cape Espenberg on Alaska's Seward Peninsula.
The object has a rectangular bar connected to a broken circular ring. It's about 2 inches long and 1 inch wide. It was found in August at a home site dug into a beach ridge.
"The whole plan was to look at how subsistence and social practices changed over about 500 years in time," he told The Associated Press.
The work in summer 2011 was the third and final complete season for the project. Analysis of animal bones and wood objects including boat parts will follow.
"We're trying to figure out if the people were whaling," Mason said Monday. "That's a big topic. The wood is a big story. We have to get more radiocarbon dates, more tree ring dates. We're going to figure out the climate story from the wood."
The bronze artifact was found in 3 feet of sediment near the entryway to the house by a University of California, Davis, doctoral student, Jeremy Foin, as he used a sifting screen. Beveling on one side of the bronze and the concave shape of its other side indicated the item had been cast in a mold.
A copper needle was found at another Cape Espenberg house. Early Alaskans were known to hammer copper into tools but there is no known metal casting in Alaska, Mason said.
"It would be incredibly significant if there were metallurgy in Alaska, but I just don't see that being here," Mason said.
The house site is within the Bering Land Bridge National Preserve and the origin of the piece more likely was Korea, China, Manchuria or southern Siberia. Early Inupiat Eskimos in northwest Alaska might have brought the object from the other side of the Bering Strait about 1,500 years ago, the researchers said, and passed it down through generations.
A piece of leather wrapped around the rectangular bar gave a radiocarbon date of about A.D. 600.
"That seems early based on what we know presently about the house, but we haven't dated the house well enough to be confident that our previous thoughts about the house are correct," Mason said.
One Asia archaeologist suggested the piece may have been part of a harness or horse ornament. The researchers are looking for an East Asia expert to confer with on the bronze piece.
Mason said it's not likely the bronze piece was washed ashore after being dropped by a Russian explorer or a whaler.
"That's totally unlikely, in fact nearly impossible, considering where it is," he said.
The excavated home was an inauspicious mound that was part of a marsh in a sand dune away from the current coast.
Purdue University Assistant Professor H. Kory Cooper, prehistoric metallurgical expert, will study the bronze piece, Mason said.
Researchers recovered several thousand artifacts at Cape Espenberg, including harpoons used to kill seals, fishing spears and fishing lures.