ECU Europa

The ECU was never legal tender in the conventional sense — it existed as a unit of account within the European Monetary System from 1979, used for interbank settlements and denominating EU budget transactions, but never issued for general circulation by any central authority. These collector pieces, produced by various European mints in the 1990s in anticipation of monetary union, occupy an awkward legitimacy gap: official enough to carry national authorization, unofficial enough that X# references rather than KM numbers are the honest cataloging choice.

The ECU was formally replaced by the euro at a 1:1 rate on January 1, 1999.