Koch, an Art Deco amethyst, moonstone, pearl and diamond sautoir, 1920s, the fancy-link platinum

Koch, an Art Deco amethyst, moonstone, pearl and diamond sautoir, 1920s, the fancy-link platinum chain threaded with pearls and carved amethyst and moonstone links accented with rose-cut diamond roundels, suspending a fluted amethyst drop with a rose-cut diamond and calibré-cut amethyst surmount, chain length 62cm, pendant length 4.5cm, signed Koch