Solution : https://service.sap.com/sap/support/notes/336231 (SAP Service marketplace login required)
Key words : 
possibly annoying dialog box, mn635 scale currency &1 earmarked, mn636 condition currency &1 earmarked, mn634 arrangement currency &1 earmarked, invalid rebate arrangement currency, condition-based currency, terms subsequent settlement, european monetary union, volume-based rebate, rebate arrangement currency
Related Notes : 
       
| 400432 | Expiring currencies, rebate arrangmnt maint. (purch., sales) | 
| 183379 | Composite SAP note subsequent settlement (Purchasing) 4.6 | 
| 152725 | Collective note: Subsequent settlement (Purch.) Release 4.5 | 
| 104668 | Collective note: Subsequent settlement (Purch.) Release 4.0 | 
| 40147 | Collective note: Subsequent settlement (Purch.) Release 3.0 |