currency Currency

Type of currency in which the price is presented.

Usage/Remarks

Best Practice

Although this is an optional attribute, best practice is to include it for every price where it is known. The attribute can take any value, but best practice is to use the ISO 4217 “currency code” values. These are 3-letter, all upper case codes that are NOT the same as the ISO country codes. Examples include:
USD
United States Dollar in the US and US territories
CAD
Canadian Dollar
EUR
European Union Euro
RUB
Russian Ruble
These codes are defined by ISO in ISO 4217 and listed at: https://www.currency-iso.org/en/home/tables/table-a1.html
OPTIONAL on element: <price>
Value Meaning
Text, numbers, or special characters An abbreviation for a currency, typically using the ISO 4217 three-letter alphabetic codes, for example, “USD” for the United States Dollar.
Restriction @currency is an optional attribute; there is no default.
Tagged Sample

<price>

The @currency attribute should use the ISO 4217 three-letter currency codes.
...
<product product-type="book">...
 <publisher-name>Wildside Books</publisher-name>, Rockville,
 MD, 2010, Price: <price currency="USD">$4.99</price>. ISBN:
 <isbn>1557426805</isbn>, <size units="pages">330</size> p.
 (paperback)</product>
...