Stunning antique CARTIER ruby and diamond ring

AN ANTIQUE CARTIER RUBY AND DIAMOND CLUSTER RING in 18ct yellow gold, set with an oval cut ruby of approximately 1.00 carats in a cluster of pear cut diamonds, the diamonds totalling 2-2.5 carats,the ring is numbered, French assay marks,with French maker's mark of Cartier, size M1/2 / 6.5, 5.3g.