The currency in which the monetary amount is expressed.<br/><br/>
Use standard formats: <a href="http://en.wikipedia.org/wiki/ISO_4217">ISO 4217 currency format</a>, e.g. "USD"; <a href="https://en.wikipedia.org/wiki/List_of_cryptocurrencies">Ticker symbol</a> for cryptocurrencies, e.g. "BTC"; well known names for <a href="https://en.wikipedia.org/wiki/Local_exchange_trading_system">Local Exchange Trading Systems</a> (LETS) and other currency types, e.g. "Ithaca HOUR".