A rare Edwardian diamond sway pendant from c.1910 that was stolen in the Oxfordshire theft.
The owners were away, but the theft was discovered by the housekeeper on September 11.
The thieves smashed a 4ft hole through a brick wall before forcing their way into the strongroom in the basement where the objects were kept.
Police are investigating and the officer dealing with the matter is DS Alun Watkins. Anyone with information should contact the police enquiries centre on 01845 8505505 quoting the crime reference number: MT3175125
