1) This result is from sqlplus, having set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P15
2) Yes, but in sqlplus, not in SqlDeveloper
3) In SqlDeveloper, no change. I still don't know if it is affected by the NLS_LANG environment variable.
4) Yes, both seem to give me the same results
5) Yes. On sqlplus, chr(0164) returns ñ, chr(207) returns ¤ (correct). On SqlDeveloper, chr(0164) returns the Euro Symbol, chr(207) returns Ï.