For me it is the historic connection. Particularly, how coins form an unbroken continuum of history from the present day, right back to the time when coins were invented 2600 years ago.
Coins are one of the few ancient inventions that we still use today. If you were to get yourself a time machine, go back in time to ancient Greece or Rome, kidnap a random citizen, and bring them forwards to our time, they'd be totally confused by everything they saw around them - the technology, the culture, the food, the language, it would all be utterly alien to them. But give them some coins, and they would not only know exactly what they were (even if they couldn't read the language) but they'd also know how and when to use them.
Coins also form important historical and archaeological evidence, just by their mere existence. Just one example: the Roman empress Severina. You will notice that her Wikipedia article has pictures of coins, and nothing else - that's because she is known from her coins, and only from her coins - there is no other surviving physical evidence (no tomb or statues) and the historical written records are almost totally silent about her, only referring to her dismissively as "Aurelian's wife". The coins are the only evidence of her name, or her physical appearance. The coins even hint that, after her husband's death, she may have ruled Rome briefly in her own right before the next emperor was selected - a possibility that simply wouldn't have occurred to anybody without the numismatic evidence.
Coins are one of the few ancient inventions that we still use today. If you were to get yourself a time machine, go back in time to ancient Greece or Rome, kidnap a random citizen, and bring them forwards to our time, they'd be totally confused by everything they saw around them - the technology, the culture, the food, the language, it would all be utterly alien to them. But give them some coins, and they would not only know exactly what they were (even if they couldn't read the language) but they'd also know how and when to use them.
Coins also form important historical and archaeological evidence, just by their mere existence. Just one example: the Roman empress Severina. You will notice that her Wikipedia article has pictures of coins, and nothing else - that's because she is known from her coins, and only from her coins - there is no other surviving physical evidence (no tomb or statues) and the historical written records are almost totally silent about her, only referring to her dismissively as "Aurelian's wife". The coins are the only evidence of her name, or her physical appearance. The coins even hint that, after her husband's death, she may have ruled Rome briefly in her own right before the next emperor was selected - a possibility that simply wouldn't have occurred to anybody without the numismatic evidence.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis