This is a commemorative collectable 24 carat gold coin. A gold coin is a coin that is made mostly or entirely of gold. Most gold coins minted since 1800 are 22 carat gold, while most of today's gold bullion coins are pure gold. The pure gold is 24 carat. In the past gold coins were used also as circulation coins. Nowadays they are mostly used as bullion coins for investors and commemorative coins for collectors. Gold has been used as money for many reasons. It is fungible, with a low spread between the prices to buy and sell. Gold is also easily transportable, as it has a high value-to-weight ratio compared to other commodities such as silver. Gold can be re-coined, divided into smaller units, or melted into larger units such as gold bars, without destroying its metal value. The density of gold is higher than most other metals, making it difficult to pass counterfeits. Additionally, gold is extremely unreactive chemically: it does not tarnish or corrode over time.