40005298, Marlborough, 531, Facing lion's head., Sotheby's, London, Boardman, J., Scarisbrick, D., Wagner C., Zwierlein-Diehl, E: The Marlborough Gems (2009), Story-Maskelyne, M.H.: The Marlborough Gems (1870), 16 December 2020, lot 18, cameo, Cat's eye