French retro sapphire and diamond terraced bombe cluster ring

French retro sapphire and diamond terraced bombe cluster ring in 18kt yellow gold. Centred with an oval mixed cut sapphire in a rubover setting, encircled by a row of twelve round brilliant cut diamonds in grain settings, to an oval cluster surrounded by deeply incised concentric ribbing to the gallery and continuing down the shoulders before smoothing to a solid shank. Hallmarked 18kt gold, French.