1943 Copper-alloy Penny

Some coins gain extra value because of mistakes or imperfections in their minting. The most famous of these is the 1943 copper-alloy penny. During the Second World War, U.S. pennies were struck in steel as a result of copper shortages. However, a small number of 1943 pennies were accidentally struck using leftover copper-alloy coin blanks. A 1943 copper cent sold for $1.71 million . Because of this coin's high value, it is often counterfeited.

1933 Double Eagle

The rarity of a coin is based on its age. In other cases, a coin can be rare simply because of history. This is the case with the 1933 $20 gold double eagle. This coin was released only shortly before the U.S. discontinued its federal gold standard. As a result, the coin was never circulated and most were destroyed. The surviving examples are therefore extremely rare. A 1933 double eagle was sold in 2002 for $7.65 million.

Anglo-Saxon Gold Mancus

Finds of historical coins can be as valuable as all but the rarest collectibles. In 2007, the British Museum acquired an early-9th-century gold coin for approximately $586,000. The coin, minted in the name of King Coenwulf of Mercia, was discovered in Bedfordshire in 2001 by a metal detector enthusiast out walking with his dog. It is one of only a handful of Anglo-Saxon gold coins. Silver coins, although still rare, are much more common.