Research indicates that this is a late Victorian shell cameo brooch  representing Hebe, the goddess of youth, feeding her father transfigured as an eagle.

 

Similar representations can be found on other cameos of that period.

 

The cameo is mounted on a gold coloured metal frame with a pin and C clasp.  I have not found any marks stamped on the frame to indicate what is the metal.

It measures approximately 60 x 50 mm and weighs 18.4g.

 

Postage: UK £2.50  - 1st Class signed for