I for one don't remember what it was.
examples:
Content-Type: Text/Plain; charset=unicode
Content-Type: Text/Plain; charset=unicode-chinese
Content-Type: Text/Plain; charset=unicode-japanese
Content-Type: Text/Plain; charset=unicode-korean
Content-Type: Text/Plain; charset=unicode-everything
Surely, you miss several things.
You forget Devanagari.
You also forget the problem on how "charset" be defined.
Use the "unicode" charset when you don't care how the message looks.
It should be removed because it is effectively useless and introduces
confusion on the following definition of what "charset" is.
(d) Character set issues
The Working Group specified the definition of a character set
for the purposes of quad-x to be a unique mapping of a byte
stream to glyphs, a mapping which does not require external
profiling information.
Why, do you think, each national instance of ISO 646 is separated?
If one use some character, he surely expects it be displayed
correctly.
Or, shall we provide such thing as:
charset=local-ascii
in which you can't expect curly braces displayed as curly braces?
Masataka Ohta