It's called a mint mark and means the nickel was minted in Denver, and was made in 1964 or earlier.
US Coins dated 1965-67 didn't carry mint marks due to the so-called Great Coin Shortage of the 1960s. Mint marks were resumed in 1968 but were moved to the front sides of coins, usually near the date.
Other possible mint marks on modern coins include
monticello
The nickel. Monticello was Thomas Jefferson's home so it nicely complements his image on the front of the coin. Of course, if you look at the nickel you'll see that the building has the name MONTICELLO right underneath the picture!
1951 is a common date. In average condition most are worth 10 to 30 cents. A 1951 nickel with an S mint mark next to Monticello would retail for about 50¢ if it was only slightly worn.
With no mint mark next to Monticello, or a "D", it's worth about a dime assuming average condition. If there's a small "S", it's worth about a quarter.
It's Monticello, Thomas Jefferson's house. The name is written directly under the image.
monticello
buffalo
The nickel. Monticello was Thomas Jefferson's home so it nicely complements his image on the front of the coin. Of course, if you look at the nickel you'll see that the building has the name MONTICELLO right underneath the picture!
Monticello
1951 is a common date. In average condition most are worth 10 to 30 cents. A 1951 nickel with an S mint mark next to Monticello would retail for about 50¢ if it was only slightly worn.
With no mint mark next to Monticello, or a "D", it's worth about a dime assuming average condition. If there's a small "S", it's worth about a quarter.
The US nickel (five cent coin) has an image of Jefferson's home, Monticello, on the back.
It's Monticello, Thomas Jefferson's house. The name is written directly under the image.
The US 5 cent coin (a nickel). That is his home- Monticello- on the back.
The presence of the word Monticello under the building indicates it's an image of Thomas Jefferson's home on the other side of a nickel.
The third U.S. President, Thomas Jefferson, is on the nickel. His home, Monticello, is on the back of the coin.Thomas Jefferson.
Monticello is the home of the president shown on the coin's front side, Thomas Jefferson.