LELAND, Mich. (AP) — More than three weeks later, a northern Michigan sheriff is calling it a mystery: A man's body in a heavy coat remains unidentified after it was discovered in Lake Michigan.

The body of a white man was found on July 4, about a mile (1.61 kilometers) from Leland Harbor in Leelanau County, a popular summer destination. The man drowned and appeared to be between 50 and 70. He had no identification.

A small rubber boat was discovered about 8 miles (12.8 kilometers) from the body, but any connection is unknown. The sheriff's office released a photo of the boat and a sketch of what the man probably looked like before his death.

"Nobody's made any inquiries" about a missing relative, Sheriff Mike Borkovich said Thursday. "We're all frustrated. We want to be able to identify this individual to provide dignity for him and give his family closure. Somebody somewhere knows who he is."

The man's clothing was all black, and he was wearing a heavy coat. A money clip had less than $50.

The man had extensive dental work. Borkovich said anyone who knows him might be able to lead investigators to a dentist who could help confirm an identity. A fingerprint is being analyzed, too.

Anyone with information can call (231) 256-8800.