CoA, or Certificate of Authenticity, is a document that verifies the legitimacy of an item, often used in the art and collectibles market. It provides proof that a piece is genuine and not a reproduction or counterfeit. This certificate typically includes details about the item, such as its origin, artist, and any relevant history. In addition to art, CoAs are commonly associated with sports memorabilia, antiques, and collectible items. They help buyers feel more confident in their purchases by ensuring that the item has been properly authenticated by a reputable source.