The value of a coin can vary depending on several factors such as rarity, condition, age, historical significance, and demand. Here are the top 5 most valuable coins in the world as of my knowledge cutoff in 2021:

1. 1933 Double Eagle – This is a $20 US gold coin that was minted in 1933 but never circulated due to the gold standard being abandoned in the US during the Great Depression. Only a few were known to exist, and they were considered illegal to own until the US government authorized their sale in 2002. One sold at auction for over $7 million in 2002, making it the most valuable coin in the world.
2. 1794 Flowing Hair Silver Dollar – This is the first silver dollar minted by the US federal government in 1794, and only 1,758 were produced. One sold at auction for over $10 million in 2013.
3. 1787 Brasher Doubloon – This is a gold coin minted by goldsmith Ephraim Brasher in 1787, and only a few are known to exist. One sold at auction for over $7.4 million in 2011.
4. 1343 Edward III Florin – This is a gold coin minted by King Edward III of England in 1343, and only three are known to exist. One sold at auction for over $6.8 million in 2006.
5. 1933 Saint-Gaudens Double Eagle – This is another $20 US gold coin that was minted in 1933 but never circulated. A few were known to exist, and one sold at auction for over $4 million in 2002.

Please note that the value of these coins can change over time due to fluctuations in the market and other factors.