40005085, Marlborough, 463, Portrait (profile right): Oliver Cromwell. Laureate head of the Lord Protector Oliver Cromwell., Unknown, Boardman, J., Scarisbrick, D., Wagner C., Zwierlein-Diehl, E: The Marlborough Gems (2009), Story-Maskelyne, M.H.: The Marlborough Gems (1870), no. 463, Bluish chalcedony