Set with a dark orange carnelian intaglio engraved with four oxen, it was taken after a case was forced open along with a late 13th or 14th century gold ring with a twin bezel set with a turquoise and a garnet.
If you have any information please contact PC Stephen Linton at Taunton Police Station on 0845 4567000 or Crimestoppers on 0800555111.
Police are also still appealing for information about the seven William De Morgan ceramics stolen from the De Morgan Centre in south west London.
The six trademark lustre decorated dishes and one 18in (47cm) high twin-handled urn were taken after a break-in during the early hours of the morning on July 29. A reward of up to £15,000 has been issued.
Anyone with information should contact Detective Constable Michelle Roycroft of the Metropolitan Police art and antiques unit on 0207 230 2150 quoting the crime reference number 0319719/07 or Mark Dalrymple of loss adjusters Tyler and Co on 0207 377 0282.
Stolen: medieval rings and De Morgan ceramics
Pictured here is a 16th century gold ring that was stolen from Somerset County Museum in Taunton on either August 6 or 7.
