\def\grafix#1,#2,#3,#4{
   \setbox1\vbox{\centerline{\vbox to#1{
      \hbox to#2{\special{position,include #3}\hss}\vss}
   }}
   {\vbox{\ifnum#4>0\hrule\fi
      \hbox{\ifnum#4>0\vrule\fi\hskip 1pt
         \vbox{\vskip 1pt
            \box1
            \vskip 1pt}
         \hskip 1pt
      \ifnum#4>0\vrule\fi}
   \ifnum#4>0\hrule\fi}}}

This is a test of how some graphics might be centered in the file itself.
It may not work, but it is worth a try.

\grafix 2.3truein,2.3truein,{pseal.tex},0

Then again, it might.  We shall see, we shall see.  This is Tomas Rokicki,
signing off.
\bye