40004552, Marlborough, 138, Poseidon standing on the prow of a ship holding a dolphin and trident. Ground line; inscribed below, CL.SVP., CL.SVP., Unknown, Boardman, J., Scarisbrick, D., Wagner C., Zwierlein-Diehl, E: The Marlborough Gems (2009), Story-Maskelyne, M.H.: The Marlborough Gems (1870), no. 138, Aquamarine