Editing ISO 4217 (section)

=== <span class="anchor" id="XXX"></span><span class="anchor" id="X currencies"></span>X currencies (funds, precious metals, supranationals, other) ===
In addition to codes for most active national currencies ISO&nbsp;4217 provides codes for "supranational" currencies, procedural purposes, and several things which are "similar to" currencies:
* Codes for the [[precious metal]]s [[Gold as an investment|gold]] (XAU), [[Silver as an investment|silver]] (XAG), [[Palladium as an investment|palladium]] (XPD), and [[Platinum as an investment|platinum]] (XPT) are formed by prefixing the element's chemical symbol with the letter&nbsp;"X". These "currency units" are defined as one [[troy ounce]] of the specified metal.
* The code XTS is reserved for use in testing.
* The code XXX is used to denote a "transaction" involving no currency.
* There are also codes specifying certain monetary instruments used in international finance, e.g. XDR is the symbol for [[special drawing right]] issued by the [[International Monetary Fund]].
* The codes for most [[Supranational currency|supranational]] currencies, such as the [[East Caribbean dollar]], the [[CFP franc]], the [[CFAF|CFA franc]] BEAC, and the CFA franc BCEAO. The predecessor to the euro, the [[European Currency Unit]] (ECU), had the code XEU.

The use of the initial letter "X" for these purposes is facilitated by the [[ISO 3166#Codes beginning with "X"|ISO&nbsp;3166 rule]] that no official country code beginning with X will ever be assigned.

The inclusion of the EU (denoting the [[European Union]]) in the [[ISO&nbsp;3166-1]] reserved codes list allows the [[euro]] to be coded as EUR rather than assigned a code beginning with X, even though it is a supranational currency.