An early 20th century circular diamond seed pearl and black onyx-set pendant

An early 20th century circular diamond seed pearl and black onyx-set pendant, the pierced lattice millegrain-set with diamonds and seed pearls, mounted in a circle of seed pearls, quartered with black onyx in platinum, suspending from a conforming platinum fine-link neck chain set with diamonds and seed pearls, 3.5cm wide, chain 72cm long