19th century Cameo on agate, gold and diamond

Cameo on pink agate depicting a young woman in profile looking to the left. The artist has finely carved the white vein of the agate to reveal this delicate profile. This young woman is represented in an antique costume. The young woman has her hair up in a bun and is wearing a tiara. The cameo is set in a white gold frame with diamonds. The setting is decorated with shells set with diamonds, one of which is enhanced by a fine pearl.
Gold hallmarks: eagle head.
Dimension with the pendant: 2.55in. (6,5 cm).
Dimension without the clasp: H: 2.16in. (5,5 cm); L: 1.18in. (3 cm); W: 0.39in. (1cm).
Second part of the 19th century.