Instructions
Look for markings that determine if the artifact is Union or Confederate. Confederate items are usually more crude than Union items, and some were from Great Britain. Look for the "British Enfield" logo on Confederate items. Some items, like belt buckles, will contain letters. "CSA" stands for Confederate States Army and the bold letters "US" stands for the United States.
Look for oxidation or "patina" of metal-based items. An extremely thick layer of white oxidation typically covers authentic Civil War bullets. Place a Civil War bullet in a cup of water for two hours to verify if the patina -- and therefore the bullet -- is authentic. If the patina comes off in the water, chances are the relic is a fake. Patina on fake items is also extremely thin and can flake off with pressure from a fingernail.
Read and consult reference books specific to the Civil War artifacts. Compare the artifact in a reference book to the Civil War artifact you are attempting to identify. For example, the rare (out of print) 1976 bicentennial edition of "Record of American Uniform and Historical Buttons" by Aphaeus S. Albert contains a treasure trove of detailed information on American military buttons. One section identifies Civil War era uniform buttons.
Look for inconsistencies and other markings that determine if the artifact is a reenactment prop. Reenactment pieces do not feature patina and are unlikely to show any true signs of aging.