Double Cameo of Lady with Monster on Head - what does it mean?

by Thomas
(London, UK)

The first photo is a cameo broach which was sold for $6,250 at the Christies's auction in 2007.

The second photo is the one which recently came into my possession almost by chance. I sense that the artist may be the same between the two, although mine lacks luxury materials such as enamel and diamonds.

Now, my questions are:-

1. What is this theme about? Why does a lady have a monster on her head? What does it indicate?

2. How much is it worth?

Any information would be much appreciated.

Thank you very much.

Regards,

T