A late 18th century (and later) topaz demi parure

A late 18th century (and later) topaz demi parure, the closed-back silver diamond-set bows suspend interchangable pear-shaped topaz drops in yellow gold, with diamond-set hook fittings, with a matching late 18th century diamond-set silver bow brooch, suspending a larger orange topaz, earrings length 5.4cm longest, brooch length 4.5cm, fitted case