I think that John's probably right. My take on it is that we should
allow all the ISO character sets to be specified in the form ISO-IR-xxx,
but that the "default" content-type should be handled specially, because
it probably isn't, from all I've heard, exactly the same as ISO-IR-6.
We can't change the default RFC 822 body part retroactively. --
ISO-IR-6 is actually the same as ASCII, except that the control
codes are not defined in ISO-IR-6. I would go with allowing them both,
the ASCII name is especially convenient if the user is going to type
this by hand, as ASCII is very well known, and people may have
problems in remembering the relevant ISO registration number.
Keld