Antique black opal and diamond cluster ring. Set to centre with an oval cabochon natural unenhanced black opal in an open back rubover setting with an approximate weight of 2.40 carats, encircled by a single row of nineteen round old cut diamonds in open back grain and rubover settings with a combined approximate weight of 0.45 carats, to an elongated flora form featuring polished borders, framed by scalloped edging, intricate open linear gallery and fancy backholing, the inwardly tapering shoulders gently curve to a slim shank. Tested platinum, numbered '2432', circa 1915.