40004572, Marlborough, 659, Isis enthroned, wearing a crown, suckling Horus. Ground line. Engraved face., Unknown, Boardman, J., Scarisbrick, D., Wagner C., Zwierlein-Diehl, E: The Marlborough Gems (2009), Story-Maskelyne, M.H.: The Marlborough Gems (1870), no. 659, Sardonyx