Any currency notation normally reflects the value of money (ie, its purchasing power) for a particular economy at a given time, typically the time when the notation is made. This notation is known as the 'nominal value' of a currency (eg, $5). Such nominal value is not very informative in the long run, and may lead to misinterpretations (eg, $5 in 1905 had much more value and, thus, bought more things than $5 in 2010).
Nominal values can be standardized by adjusting the nominal value according to a fixed period of time, thus bringing about the 'real value (r$)' of a currency. Such 'standard value of money' is available since 2010, published in WikiofScience as referential currencies. Therefore, standard (or referential) values shall be used together with any nominal or constant values on WikiofScience pages.
Eg, The average annual salary in the U.S. was $40,712 (r$41,380) in 2009, barely higher than the $30,470 (r$39,881) it was in 1999, if we consider a decade of inflation.
The ISO 4217 letter code for a currency (eg, USD, NZD, EUR…) should be used preferentially to currency symbols (ie, $, $, and €, respectively), especially when the use of the latter may lead to misunderstandings between currencies of different countries.
Eg, rUSD 10, rAUD 10, rNZD 10, instead of r$10; rEUR 50, instead of r€50; rGBP 1 000, instead of r£1,000.