A diamond and blue glass brooch, late 18th century

A diamond and blue glass brooch, late 18th century, the oval blue glass plaque applied with a diamond posy, the central flower head mounted en tremblant, within an outer border of rose-cut diamonds in closed-back settings, a glazed locket compartment to the reverse, mounted in silver and gold, on a later gold chain, pendant length 7cm, chain length 58cm