A Renaissance carved sapphire intaglio

A Renaissance carved sapphire intaglio, depicting Julius Caesar, the octagonal sapphire 1.5cm high, mounted in a later gold ring, size P 1/2

PROVENANCE: The Marlborough Collection, formed by George, fourth Duke of Marlborough and originally believed to be from the Arundel collection. 
Later auctioned by Christie, Manson & Woods, 'The Marlborough Gems', June 28 1875, lot 381, 'An Arundel gem (Cat. Thec. A, No. 15)'. 
Subsequently auction by Christie, Manson & Woods, 'The Marlborough Gems', June 26 1899, lot 381, 'An Arundel gem (Cat. Thec. A, No. 15)'. It is interesting to note that the lot has a hand written amendment stating that it is Renaissance. 

Believed to have been owned by Mary Anne, Viscountess Hereford, (1843 – 1924) and thence by decent to the current owner.

Published: J. Boardman, C.Wagner, D.Scarisbrick, E. Zwierlein-Diehl, The Marlborough Gems: Formerly at Blenheim Palace, no 208.