Most people are familiar with the idea that certain coins are valuable in terms of money. They can be bought or sold and retain value based on their condition, scarcity, and design. However, not as many people think about the ways that coins serve history as evidence of human activity and behavior patterns, how they can establish dates for historians or archaeologists, or what they tells us about humanity’s changing values over time.

We mentioned this before when we talked about the Spanish piece of eight. The success and breadth of influence of the Spanish empire worldwide was partly due to this coin. When they found silver riches beyond imagining in Bolivia, this elevated the status of Spain relative to other countries in Europe in the world because silver was inherently valuable. It could be used to pay soldiers to fight Spain’s wars. It could be used to trade for goods and services other countries couldn’t bargain for. It could finance further exploration. The Spanish took their silver with them in coins wherever they went, and war and commerce followed. Any time a piece of eight is discovered in a dig site far, far from Spain, it tells you more about the might and influence of the Spanish.

Coins are pivotal evidence partly because they are minted from metal which does not rot over time like wood or fibers. Occasionally mummies are discovered in very dry or very cold places with their clothing and personal objects still intact due to unusual environmental conditions, but coins routinely survive burial, shipwrecks, and other natural disasters like earthquakes or floods.

Additionally, unlike jewelry, swords, or ceramics, people of lower status traded in coins. Finding a hidden coin collection or hoard can tell you information about the previous owner and the period he or she lived during. It might be a bribe or payment. It could be someone’s life savings. It could even be ill-gotten gains or stolen Confederate gold.

Coins help historians and archaeologists date things as well. The discovery of a silver Baghdad coin in a buried Viking ship in Yorkshire in 2004 helped narrow the window of time for the burial to the ninth century and told historians more about Viking activity in England during that era. Previous Viking finds were from either raids or settlements. This coin helped fill the gaps in the timeline of interaction between these two cultures.

Finally, coins can tell you about what people felt were their most important values because cultures and empires tended to put rulers, gods, or other aesthetically pleasing ornamentation on their coinage. The British empire put their ruling monarchs on their coins, but the American government made the decision not to elevate their leaders to that level, striking its first coinage with words and pictures denoting “Liberty,” the value they most cherished at the time. Ancient Roman coins depicting Venus, the goddess of Love, may reveal something about standards of beauty during the time they were minted. They also tell you about the technology of the time and what the Romans were capable of creating in terms of tangible art.

When you make an investment in coins, you are investing not just in something that can be sold or traded but helping to preserve human history. Coins tell us about what the people of the past were like, where they went, what they did, and what they thought was important. What other similarly important object might you find in your back pocket or your purse?