Numismatics the study of coinage, and is a wonderfully useful tool in the archaeologist's and historian's toolbox. One of the best things for an archaeologist to find while digging is a coin. The reason is simple; it can instantly provide some date for the layer they are digging. Additionally, coins provide information for trade, economy, social organisation, mythology, ideologies, personages, leadership, military, important events, and the list goes on.
This is a companion discussion topic for the original content at https://www.worldhistory.org/Numismatics/.