This "ancient thing" is an Oneota pottery sherd dating to approximately the 1450s. A sherd is the term used for a broken piece of ceramics or pottery, whereas a shard is a broken piece of glass. This piece of pottery is also particularly significant because it is the main diagnostic artifact type for this culture. Diagnostic artifacts are what allow archaeologists to distinguish different material cultures from one another. Oneota pieces from this time period are shell-tempered, with rounded bottoms, constricted necks, and flared rims. They can be either decorated or not, though this piece is. This piece is great because it is a large enough piece that even untrained people can pick out all of these features, unlike many smaller sherds.