Here is the response from Corning:
Dear Ms. Freeman,
Thank you for your email below. I have attached some pages that may be somewhat relevant, from the Ray and Lee Grover 1980 publication entitled ‘English Cameo Glass’.
Page 8 of this publication provides a good description of ‘dolce relievo’, while the other two pages contain a sketch (taken from George Woodall’s sketchbook), and a vase, top left (either Stevens & Williams or Thomas Webb & Sons: http://en.wikipedia.org/wiki/Thomas_Webb_%26_Sons
) that are somewhat similar by way of some of the motifs employed.
However, as it is an unsigned it might not be by Stevens & Williams or Thomas Webb & Sons, but it is in the style of.
I am sure you can appreciate how difficult it is to be certain vis-à-vis identification without actually handling the piece in person.
As for valuations, due to the fact we are a museum we cannot provide appraisals on objects.
There should be a list of valuers and appraisers/fine art dealers in your local yellow pages who may have a specialty in glass.
Another excellent publication that may be of help is the following: http://www.cmog.org/library/british-glass-1800-1914-charles-hajdamach?search=library_collection%3A8b926109a463954f5cdae2d0a23c4015&page=3
Dr. Audrey Whitty,
Curator of European and Asian Glass,
The Corning Museum of Glass,
1 Museum Way,
Direct Line: +1 607 438 5226