This was brought back by John Wesley Davis ( America's third commissioner to china,1848-1850 ) and has been in my family ever since. I have no idea what it is besides a Ch'ien lung plate.One can't see it in the photo;but two of the limbs of the central medallion were left white.

Anyone have any idea of its value? If I sell it what are the best steps to take and auction house to sell it at?

I'm also interested what Davis did during is mission to China.

http://public.fotki.com/snardles/plate/plate_back.html
http://public.fotki.com/snardles/plate/plate_front.html

Have a look at Allensantiques.com
Contact Tony Allen via the address there. He should be able to tell you more about the piece, and perhaps point you in the direction of a reputable auction house.