A coin can be worth a ton of money -- a pretty penny, one might say -- if it's rare and has enough historical significance.

The next time you decide to put all your spare change into the nearest Coinstar machine, take a moment to sift through it.

The public can get up close to over $100 million of historic rare coins and currency, including a famous $3 million nickel, at the National Money Show from Feb. 27 ...