1943 Lincoln Head Copper Penny:
In 1943, due to the need for copper during World War II, the U.S. Mint produced pennies using steel coated in zinc. However, some were mistakenly made from copper.
2004 Wisconsin State Quarter With Extra Leaf:
Thousands of 2004 Wisconsin quarters feature an additional leaf on a husk of corn, speculated to be caused by a Mint employee. Depending on quality, these "extra leaf" coins have sold for up to $300.
2009 Kew Gardens 50P Coin:
In 2009, the Royal Mint issued only 210,000 50p coins commemorating the 250th anniversary of the Royal Botanical Gardens at Kew. Featuring the Kew Gardens Pagoda, these coins can fetch about $313 on eBay.
1955 Doubled Die Penny:
The 1955 doubled die penny exhibits a slightly misaligned image due to minting errors. Around 20,000 to 24,000 of these coins were released, primarily from cigarette vending machines.
2005 In God We Rust Kansas State Quarter:
Grease build-up in the coin die during minting resulted in the word "Trust" being partially filled, creating the error "In God We Rust." While not funding a retirement, collectors may pay extra for this unique error, offering a modest return.
2000 Australian $1/10 Mule:
Due to a printing error, some Australian $1 coins featured the Queen Elizabeth II obverse intended for 10-cent pieces, creating a "mule." Collectors may pay a few hundred dollars for these double-rim coins.
2008 Undated 20P Coin:
In November 2008, the Royal Mint omitted the date on between 50,000 and 250,000 20p pieces, making them a curiosity rather than a fortune, though finding one may still net $100.
1982 No Mint Mark Roosevelt Dime:
In 1982, the Philadelphia Mint omitted their identifying mark on some Roosevelt dimes, a first for U.S. coins. While thousands were released, these dimes can sell for $50 or more in excellent condition.
1997 Double-Ear Lincoln Penny:
An anomaly on the 1997 penny appears to give Abraham Lincoln double ear lobes, making it a sought-after collector's item fetching up to $70.