An 'Essex crystal', ruby and diamond brooch, late 19th century, the centre set with a reverse-carved

An 'Essex crystal', ruby and diamond brooch, late 19th century, the centre set with a reverse-carved and painted rock crystal intaglio depicting a lady riding sidesaddle on horseback, backed with mother of pearl, bordered with rose-cut diamonds and cushion-shaped rubies, mounted in silver and gold, diameter 2.9cm, indistinct assay mark, case