Own a Mysterious Artifact? Go Show It to a Scientist

R. Mickens/American Museum of Natural History via Flickr These girls learned in 2011 that they were the owners of a sedimentary pudding stone (left) and a trilobite.

Life is full of mysteries. Some lives are full of mysterious objects. The necklace-looking thing you found on the beach that looks as if it probably came from an animal or maybe a plant. That rock your grandfather always told you was a meteorite. The dead turtle in a box on your desk â€" bog turtle or box turtle?

Some people prefer their mysteries unsolved. For the rest, there is Identification Day, the American Museum of Natural History’s annual spoiler fest at which museum scientists and anthropologists examine your find and tell you what it actually is, or might be.

This year’s ID Day is tomorrow, May 11, from noon to 4 p.m.

There are some ground rules. Please do not bring mammal or herpetological specimens, alive or dead (photos are fine). Bring only plants you have permission to collect. Do not bring gemstones, and do not ask that your object be appraised. This is not “Antiques Roadshow.”

Andy Newman/The New York Times Do not bring in that dead turtle in the box on your desk, but do feel free to bring in a photo of it.

Scientists will also be showing off some objects from the museum’s own collections that are normally kept out of sight, including birds that Theodore Roosevelt himself collected.

In the past, museum officials said, the scientists have identified someone’s 100-million-year-old Brazilian fish, which somehow found its way into a backyard in Hackensack, N.J. Another visitor brought in what turned out to be a fossilized walrus skull, found on a beach in Virginia.

“One of my favorites is someone found a hand ax in their summer camp in 1963 that was identified as being 2,000 to 3,000 years old,” said Kira Lacks, senior public programs coordinator for the museum.

On the other hand, the news may not be what you hoped to hear.

“What’s found very often at our anthropology table are arrowheads,” Ms. Lacks said. “Sometimes you’ll flip them over and it’ll say ‘Made in China,’ but sometimes they are identified as quite old.”

You never know.