Employees and volunteers at the Atwood House Museum in Chatham are used to handling artifacts, but they’re not exactly accustomed to discovering them. That changed last week, according to the director of the Chatham Historical Society, which operates the museum. Landscapers were raking leaves on the property’s edge when they made an unusual discovery: A human skull.

They called police, who then called in state investigators.

“Within a couple of hours, they determined it was old — more than 100 years old,’’ said Danielle Jeanloz, executive director of the historical society.

The skull, which was mostly intact, was sent to the chief medical examiner’s office, Jeanloz said. Felix Browne, communications director for the Executive Office of Public Safety and Security, confirmed that the state’s forensic anthropologist was examining it.

Chatham police declined to comment, and the Cape and Islands district attorney’s office didn’t immediately return a request for information.

The quick determination meant the museum did not qualify as a crime scene.

“A lot of questions came to my mind because this is a nice, safe community,’’ she said. “Then I became fascinated.’’

There’s speculation that it could be a Native American artifact because there are numerous Native American burial sites in town, Jeanloz said. There was no indication it was an artifact related to the museum.

Another possibility Jeanloz could consider was that one of the Atwoods — who built the home in the 1750s — was buried there, which is unlikely.

One of the more peculiar aspects of the discovery was that it was found above ground. Investigators are working to determine if it was placed there by natural causes, or if an animal placed it there, Jeanloz said.

The discovery invigorated the museum’s employees and volunteers. They had been considering doing an archeological dig, and that idea has gained some steam, Jeanloz said.

“It was really a casual conversation, initially, and now all of a sudden the conversation has become very lively,’’ Jeanloz said. “We never expected to find a skull in our backyard.’’

Dylan McGuinness can be reached at dylan.mcguinness@globe.com. Follow him on Twitter at @DylMcGuinness.