PHILADELPHIA — A stoneware jug with white porcelain eyes and bared teeth is heading to a museum in the city where it was unearthed six decades ago, with historians calling it a rare artifact made in South Carolina by some of the last African slaves brought to America.

Robert Strang, a plumber, unearthed the 10-inch-tall jug in 1950 while digging a sewer line in Philadelphia's Mount Airy section. He took it home, thinking it might be an Indian relic, and never learned its history before his death in 2002.

But researchers now say it is one of only about three dozen mid-19th century "face jugs" known to still exist. So rare is the find, in fact, that the PBS "History Detectives" series plans an episode on the jug.

Strang's granddaughter, April Leopold Hynes, said she found the jug in a kitchen cupboard in October while helping her mother and aunt move from their Montgomery County home. She found similar jugs on the Smithsonian Institution's Web site, and later got in touch with John Michael Vlach, a George Washington University professor of American studies and anthropology.

Still a mystery is how the jug made its way from the South to the City of Brotherly Love.

David Barquist, curator of American decorative arts at the Philadelphia Museum of Art, says the jug will be on loan to the museum for display later this year.