The 1343 Edward III Florin

An oldie and goldie is another of the world's most expensive coins. The 1343 Edward III Florin is one of just three gold coins of this kind known to survive. The British Museum in London has two instances, both of which were discovered in the River Tyne in 1857. In 2006, a prospector using a metal detector discovered the third coin.

The front of the coin depicts King Edward III on his throne, flanked on either side by two leopard heads, while the reverse depicts the Royal Cross inside a quatrefoil. The coin is also known as the Double Leopard because of its design.

The coin discovered in 2006 was auctioned for 480,000 pounds, or roughly $850,000, setting a record for a British currency at the time. The coin is currently thought to be worth roughly $6.8 million.

Price: $6.8 million