If you collect American coins, which of these coins is impossible to obtain?

If you want to collect American coins, there is one year you'll never see on an authentic U.S. one-cent coin: 1815. That’s because we used to get the copper for them from an English supplier, but the War of 1812 that pitted us against the U.K. stopped those shipments. The mint ran out of copper in late 1814, and by the time shipments resumed in late 1815, it was too late to mint pennies with 1815 on them. In addition to the copper shortage, people also hoarded precious metals during the war.

The others are obtainable.

Although Americans now only see fractions of a cent at gas stations, they used to be much more common. From 1793 to 1857, the U.S. Mint produced a half-cent—the smallest value coin in American history.

Before nickels existed, the U.S. Mint produced an entirely different five cent coin known as the half-dime. From 1792 to 1873, silver half-dimes were produced to fill the gap between pennies and dimes, because no one likes a pocket full of pennies.

The shortest-lived circulated coin in U.S. history, the twenty-cent piece only lasted from 1875 to 1878.