howto find out the database character set

Suppose you were to enherit a database as an DBA and you suspect the database was created with US 7 bit ascii, how could you verify that? The reason is that users can not insert German special characters into to an VARCHAR2 field. The NLS_LANGUAGE parameter in the INITSID.ORA is not the solution because changing it (per session) to GERMAN does not help. Does one have to fear the worst? i.e, recreate the database to fix the problem?

There seems to be no dictionary view that tells which character set the DB was created with. But I'd be delighted to be proved wrong.

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