Onyx and diamond pin. The head is set with a rectangular onyx to centre in an open back rubover setting encircled by a cluster of twenty eight round old single cut diamonds with an approximate combined weight of 0.50 carats in open back grain settings, to an elongated oval form with millegrain border. All set to an open work structure with intricate square backholing. The reverse is fitted with a supportive cross bar with pin, approximately 7.5cm in length. Tested platinum, marked 'CARTIER NEW YORK', American, circa 1920.