A number of factors can make a coin collectable, valuable or rare. Age can be a major factor; some of the earliest minted coins can be extremely valuable. For a coin dated as recently as the 20th Century to be rare or valuable, it often needs to have been minted erroneously somehow or have an interesting story behind its minting.
1943 Copper Penny
Struck in error during World War II, the 1943 copper penny should have been made of zinc-coated steel. For the purposes of the war effort ,copper alloys were not being used to mint 1943 pennies. A few copper penny blanks are thought to have been left in the machine, so a limited number of 1943 pennies were made of copper. Only 40 of these coins are thought to exist today and have been known to sell at auction for up to £53,625.
1913 Liberty Head V Nickel
The Liberty Head V nickel is one of the rarest, most valuable coins in the world. Only five coins are known to exist and much mystery surrounds why they were made. The coins feature a profile of Lady Liberty and the year 1913 on one side and a capital V on the other. It is thought that a mint employee created these coins on a whim and they did not surface until six years later. A single coin has been recorded as selling for £1.9 million at auction.
1974 Aluminum Cent
If a coin collector has a 1974 aluminium cent, they are fortunate and actually should not even have it. During the early '70s, the price of copper was high and a plan to switch to aluminium for minting pennies was set in motion. The process got to the point where 1.5 million coins were minted. Legislation to change the substance pennies were made of failed however, and the coins were recalled to be destroyed. Some of the coins were given to U.S. senators at the time and in 1982, one resurfaced. The mint classifies these coins as unreleased and sole property of the mint itself.
1933 Double Eagle
The 1933 Double Eagle coins were minted just prior to President Franklin D. Roosevelt switching the U.S. from the gold standard. The coins were all recalled to be destroyed, but 10 are known to have evaded the original recall. Of these, nine were either seized or handed into the U.S. Secret Service during the '50s and '60s to be destroyed. The tenth surfaced in 1996 and was seized by the Secret Service. The government did not destroy this last coin and actually placed it up for private sale in 2002. The coin was sold for £4.9 million.