Please See Photos! Please take a good look at the cabochon shape.  The cabochon is a quintessential shape associated with Whiting and Davis. The coloring of the stone I have seen in Whiting and Davis Brooches.  However I can not find any Whiting and Davis Setting exactly like the one you see in the photos. So I believe this is Whiting and Davis But as the item is not marked and know different companies use the same cabochons , One just cannot be certain this is Whiting and Davis. The Brooch is not marked.