Old currency refers to money that was used in the past but is no longer in circulation. This can include coins and banknotes that have been replaced by newer designs or denominations. Collectors often seek out old currency for its historical value, as it can provide insights into the economic conditions and cultural aspects of the time it was used. Many countries have transitioned from old currency to modern forms, such as the Euro in Europe or the U.S. dollar in the United States. Some old currencies may still hold value among collectors, while others may be considered obsolete and have little to no monetary worth today.