Portrait of a Man (Robert Knox?)

Inscribed at lower left in pen and black ink: Captain Knox; at lower center in graphite, partly effaced: Capt. [period under "t"] Knox; (signed with initials?) at lower right: RW.; on verso in center in graphite: Capt. [period under "t"] Knox; at lower right of decorative border in graphite: R. White Fect. [period under "t"]; on album sheet beneath decorative border in graphite: Captain Robert Knox born about 1641 Cousin / to Strype the historian - Imprisoned 19 1/2 years / in Ceylon of which place he published / the first account; beyond upper left corner of decorative border: x 3; beyond upper right corner of decorative border: 3.