When the Seven Kingdoms first united, they agreed on a common system of coinage to promote free trade between them. Four coins were established, and each Kingdoms minted its own designs of these coins. Although the Kingdoms are no longer united, they still follow these rough values and designs in terms of their coins.
The lowest form of coin is the copper penny, also known as a common.
The next coin is the silver shilling, also known as a mark (believed too be short for market or merchant). Each shilling is worth 10 pennies.
The golden crown is the next coin, and these coins are also referred to as nobles. Each crown is worth 10 shillings or 100 pennies.
The highest coin of the Seven Kingdoms is the platinum sovereign, also known as a royal. These are rarely minted these days, usually only during the first year of a new king’s coronation. One sovereign is worth 100 crowns, 1,000 shillings, or 10,000 pennies.
In the most exotic markets known, such as those in the Astral Sea or the Elemental Chaos, an even more valuable “coin” exists. The so-called astral diamonds are worth no less than 10,000 crowns each. These are only traded in extreme forms of commerce.
In reality, most of the common folk of the Seven Kingdoms don’t trade in coin. They barter services and goods with one another in an ancient tradition that long predates their kingdoms’ alliances.