A Certificate of Authenticity (COA) is a document that verifies the genuineness of an item, such as artwork, collectibles, or memorabilia. It typically includes details about the item, such as its origin, the artist or creator, and any relevant history. The COA is often signed by an expert or authority in the field, providing assurance to buyers that the item is not a replica or counterfeit. COAs are commonly used in the art world, where pieces by renowned artists like Pablo Picasso or Vincent van Gogh can be highly valuable. Collectors of sports memorabilia, such as jerseys or signed balls from famous athletes like Michael Jordan, also rely on COAs to confirm the authenticity of their items.