YAY!!!! Have finally identified this piece. It is a 14" cake plate in the LM Embassy pattern made by Sydenstricker Glass in Cape Cod.
They have quite a lot of information on their website so I thought the link might be helpful. http://www.sydenstricker.com/main.cfm?page=history.cfm
This is what they say about the process "Two sheets of glass are cut to fit a mold made out of high fire terra cotta clay. The first sheet is decorated by sifting powdered glass through a stencil. The stencil is then carefully removed, and the second sheet of glass is laid over the decorated first piece. Both are placed on a mold and put into a fifteen hundred degree kiln for five hours. At this point, the two pieces of glass fuse, assuming the shape of the mold and locking in the colored design. The kiln is then turned off until the glass is cooled, about 40 hours later".
Thanks to all who shared their thoughts.