The currency sign (¤) is a character used to denote an unspecified currency. It is often used in place of a symbol that is not present in the font in use.
The currency sign was once a part of the Mac OS Roman character set, but Apple changed the symbol at that code point to the euro sign (€) in Mac OS 8.5. In non-Unicode Windows character sets, the euro sign was introduced as a new code point. In the Unicode character set, each of the two symbols has its own unique code point across all platforms.
The symbol is available on some keyboard layouts, for example French, Danish, Norwegian, Swedish and Finnish keyboards.