postgres & server encodings

What exactly is the SQL_ASCII encoding in postgres? I have a pg installation
with an SQL_ASCII server encoding and my database (also SQL_ASCII) seems to
be able to handle all types of encodings? how is this possible? is this what
the server & db encoding needs to be set to in order to handle various
encodings?
Also is there a way of dumping data from an SQL_ASCII db to a UNICODE db.
Creating a dump and converting with a tool like iconv is probably not an
option since the data in the SQL_ASCII db has unknown/inconsistant encoding.
Please let me know as soon as possible.
Thanks.
Salem
P.S. {I sent a similar e-mail earlier which wasn't posted on the site. ??}