In numismatics, as well as in notaphily, it is customary to use the terms obverse and reverse to denote the front and back of a coin or banknote. It is not always easy to determine which is which, however.
Originally, coins used to be struck by hand, and the side of the coin that was on the anvil die was always the obverse. The side that took the hammer strike was the reverse. This distinction cannot be applied to today's machine struck coins, which no longer have an "anvil die" at all. Therefore, certain conventions have been adopted.
- If one side of a coin has a portrait, that side is the obverse. If neither side (or both sides) have portraits, then:
- If all the coins in a series have one side with a common design, the obverse side is the one that is different on each. For example, the Euro coins do not have any portraits. But since each country has its own design on one side, while the other side shares a design common to all countries, the countries' distinctive sides are considered the obverses, and the common sides are considered the reverses, by collectors. Similarly, if a country has, for example, a coat of arms (or some other common device) on its coinage, but no portrait, and the common device appears on multiple denominations, the side without that device is the obverse.
- The side that bears the name of the country is usually considered the obverse in cases where the coin meets neither of the previous two conditions.
- If none of these rules apply, but the country issues a proof set or other such special mint-issued set, the side which is considered to be the obverse by the mint will be face up in the proof coin holder
- However, collectors disagree about many of the coins that don't fit one of the categories above, (and some that do), so there is no certainty of these, though the Standard Catalogue of World Coins will give its own opinion in such cases.
Similar rules would apply to paper money.