A variety of Internet resources and books are available for consultation to help in the identification of military buttons. According to Collectors Weekly, buttons from the Civil War are especially desired and are categorized as dug or non dug, depending on whether or not they have been excavated.
This website provides information on military buttons from the eras of the American Revolution, the War of 1812 and the Civil War. This site is associated with the button-collecting business of William Leigh of Hamilton, Va.
Check out Relicman.com
Relicman showcases the Ridgeway Reference Archive, an educational catalog of button backmarks from the Civil War era. The archive is a work in progress that is periodically updated with photographs of additional Civil War button backmarks as a tool for the research of military buttons. Relicman references a button book entitled "Dating Buttons" by Warren K. Tice. The book is sub-titled "A Chronology of Button Types, Makers, Retailers & Their Backmarks."
Contact the National Button Society
The National Button Society is an organization with information on the hobby of button collecting, which includes military buttons. Some of their information is available to the public while other information is available only to members of the society..