I would like to find out about this piece.

I would like to find out about this piece.
It is about 20cms in diameter.
Is it a plate warmer?
Is the bottom section silver?
Is the maker Cocks?
What date is it?
Is it valuable?

Cheers

Dan
plate warmer maker-72.jpg
plate warmer hallmark-72.jpg
plate warmer 1-72.jpg

I’m not sure what it is, but it is not silver - the marks are pewter marks. From this site the maker is Susannah Cocks.