Font used in MicroEd

Hi,

I have just upgraded to version 3.64.01, but I am disappointed,
because, I have been always used MicroEd to view plain text messages.
But, on about half of the messages I view, the font used is not what I
selected in the Preferences.

Here is the stripped message header of a sample message whose font
used is what I set in the Preferences:

MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit


And this one uses different font when I view it:

MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit


Is it because of the character set used? If so, how do I change the
font used?

Thanks!