Euro (€) notes and coins first came into use on 1st January 2002. Some countries - such as Monaco, San Marino, Kosovo and Montenegro - though not members of the European Union, are also using the euro as their official currency. On the other hand three EU member countries did not accept the euro when it first came into being and still keep to their national currencies today. These are Sweden, United Kingdom and Denmark.*
For the record the following currencies became obsolete since 1st January 2002. The conversion rate for the euro for each participating currency is irrevocably fixed and is the only rate used for conversion either way between the euro and the national currency unit or for conversion between the national currency units.
The official abbreviation for the euro is 'EUR'. The euro conversion rates (values of national currency units to one euro (€ 1.00) ) are reproduced below for historical interest: