For me it's a counterfeit 1856
Indian Head cent. It was given to my grandfather (probably in the late 50s or early 60s) to pay off a debt. He was cheated as it was passed off as the real thing. My grandfather gave it to my father in the early 60s. He took it to a coin dealer back then who told him he thought it was counterfeit but wasn't sure. My father gave it to me around 2000. I wasn't sure by looking at the coin with 10x magnification. I then put it under a microscope and could see that the 6 was altered. I then did some further investigation and determined that is was originally an 1858. Altering an 1858 was relatively common and can be identified because the 5s are different on a 58 vs a 56. All and all it was a fun way to learn about the coin and coin collection!