It is just beautiful!
I would suggest that you contact the New England Quilt Museum in Lowell, MA. They may be interested in looking at it and I am sure that they would give him fair market value.
If they are not interested, they should be able to provide the name of someone to contact for an appraisal and suggest the best way to sell it.
Below is the link to the museums web site:
http://nequiltmuseum.org