LONDON — Researchers at Bristol University in Britain discovered a box containing materials from archaeologist Sir Leonard Woolley’s dig of the Sumerian city of Ur tucked away on top of a cupboard.

“I would classify it in the same category as ‘I found a Monet in my grandmothers’ attic,’” Tamar Hodos, a senior lecturer in archaeology, said Wednesday.

Researchers determined that the box’s contents were 4,500 years old — consisting of pottery, seeds, carbonized apple rings and animal bones

— and had come from a tomb at an excavation in Iraq that was jointly sponsored during the 1920s and 1930s by the British Museum and the University of Pennsylvania Museum.

“There’s no question that this material is from the Woolley dig,” Hodos said.

But no one knows how the material got to Bristol, which had no connection to the dig. The university is hoping for someone to step forward to help solve the mystery.