NLS_LANG for NLS_CHARACTERSET = US7ASCII - How to set it?

 I will be creating script for a database that has the following characterset, I want to export the NLS_LANG inside the script,what value can I set it to?

SQL> SELECT * FROM NLS_DATABASE_PARAMETERS ;

PARAMETER                      VALUE
------------------------------ ---------------------------------
NLS_LANGUAGE                   AMERICAN
NLS_TERRITORY                  AMERICA
NLS_CURRENCY                   $
NLS_ISO_CURRENCY               AMERICA
NLS_NUMERIC_CHARACTERS         .,
NLS_CHARACTERSET               US7ASCII
NLS_CALENDAR                   GREGORIAN
NLS_DATE_FORMAT                DD-MON-RR
NLS_DATE_LANGUAGE              AMERICAN
NLS_SORT                       BINARY
NLS_TIME_FORMAT                HH.MI.SSXFF AM

PARAMETER                      VALUE
------------------------------ ---------------------------------
NLS_TIMESTAMP_FORMAT           DD-MON-RR HH.MI.SSXFF AM
NLS_TIME_TZ_FORMAT             HH.MI.SSXFF AM TZR