NEW YORK, NY.- They arrived in a Flahavan’s porridge box, their gnarled edges tightly wedged into rudimentary, makeshift foam packaging, shaky pen marks still visible from where the sender had outlined their shape: two paddle-shaped copper ax heads, their hand-carved edges long since dulled by time — 4,000 years’ worth.

“It was addressed to me,” said Matt Seaver, an assistant keeper in the antiquities division of the National Museum of Ireland in Dublin.

So began a mystery that has befuddled the museum and its staff, which received the archaeological treasures in late June and subsequently confirmed their authenticity. The Bronze Age ax heads are a significant discovery, Seaver said. But it’s hard to say much else without the details.

“You’re talking about two early Bronze Age copper ax heads, possibly even older than 2300 B.C.,” Seaver said. “They’re intentionally placed in the ground. By archaeologically excavating the location of that find spot, you could reveal a lot more than just taking them out of the ground.”

The package was sent anonymously, accompanied by a letter explaining that the finder hoped the artifacts could be preserved at the museum. It explained that they had been found with a metal detector in County Westmeath, the geographic heart of the island and site of the kingdom of Meath. Within the county’s borders are some of Ireland’s most sacred sites, including the Hill of Uisneach, regarded as the island’s ancient center.

It’s a complicated circumstance in Ireland, where the earth is riddled with ancient treasures and rich history. Unlike some other parts of Europe and the United Kingdom, Ireland forbids the independent search or excavation of antiquities, especially via metal detector. Most countries allow the use of the machines recreationally on public land or with the permission of private owners, with preservation rules requiring finders to notify authorities if they find something archaeologically significant.

In Ireland, though, it is forbidden to use a metal detector to search for archaeological objects anywhere in the country without a permit. Such strictures most likely explain why the finder opted for a more cloak-and-dagger strategy in turning over the artifacts. After all, using a metal detector to find relics in Ireland is punishable by a fine of more than 60,000 euros or even three months in jail.

These rules leave people in natural conundrums if they turn up something worthwhile; indeed, it is not the first time such strange, anonymous deliveries have arrived at the museum’s gates. In 2016, a similar package — this time in a plain brown envelope — arrived at the museum’s Kildare Street facility, in the heart of Dublin. Inside were ax heads and Viking jewelry.

Although that package was not accompanied by a letter, museum officials believed that the objects were most likely found with a metal detector, and perhaps by a tourist or someone who was not Irish, and therefore potentially not familiar with the country’s prohibition on the machines until after the discovery.

The museum used the most recent delivery as a chance to issue a reminder on the prohibition on metal detecting — but still, it said, it hoped that the original anonymous sender might reveal his or her identity. In an effort to coax the sender forward, the museum said information about the find would be used in confidence, and only to verify the objects’ historical significance.

“We obviously don’t want a cluster of objects coming to us anonymously, because it’s a poor precedent and the law is what it is,” Seaver said. “But in this situation, we’d face it as pragmatically as we can.”

This article originally appeared in The New York Times.