Solution : https://service.sap.com/sap/support/notes/99272 (SAP Service marketplace login required)
Key words : 
additional key words, currency customizing, manual maintenance, existing customizing, prerequisites solution, currencies, introduction, notes 120420, note 99271
Related Notes : 
       
| 99271 | Curr.maintenance euro, Curr. Customizing Assistant | 
| 91481 | Customizing of currency tables for the euro |