I have the book in question, but it's going to take a few minutes or so, to get your answer for you.
On page 119 it has the following: Livery Button:- Sturdier and better made that most sportsman buttons, there were usually made in England for use by wealthy hunt clubs and families. This one was found at a Confederate site in Darien, GA
That's about all I can find. From personal experience we found two one piece silver buttons with an eagle on them. Daniel Binder identified them as being Livery buttons. We attributed them to a camp belonging to some of Longstreets men, but that was never verified.