An early 20th century emerald and diamond-set circular brooch/ pendant

An early 20th century emerald and diamond-set circular brooch/pendant of openwork design, centrally collet-set with a rectangular step-cut emerald to the 'V' shape old brilliant-cut diamond-set surround, the outer border collet-set with rectangular-cut emeralds, each separated by an old brilliant-cut and rose-cut diamond motif, various detachable fittings and miniature tool, suspended from an old brilliant-cut diamond collet and fetter link chain necklace pendant diameter 4.2cms, chain length approximately 58cm, combined weight 20.3g Condition: