YORK, ENGLAND—Scholars gathered in York last weekend to discuss an enigmatic sapphire ring found by a metal detectorist in 2009. The beaded gold piece, which is unlike any other in the museum's collection, may date to between the seventh and eleventh centuries A.D. "This beautiful ring has really got us puzzled," said Natalie McCaul, curator of archaeology at the Yorkshire Museum. A jeweler who replicated the piece attended the meeting to explain how he remade the ring, and offered insights into how the original craftsman may have fashioned the unusual artifact.