The European Currency Unit (ECU) was a basket of European Community currencies used as the unit of account before the euro was introduced in 1999. It served as the precursor to the euro and was used for intergovernmental transactions.
Example
“Before the euro launched in 1999, the ECU served as the unit of account for the European Monetary System, with its value determined by a weighted basket of member state currencies like the Deutsche Mark and French Franc.”