\font\structit cmti10 at 17.28truept
\font\structbf cmbx10 at 17.28truept
\font\structsl cmsl10 at 17.28truept
\font\structrm cmr10 at 17.28truept
\font\structsy cmsy10 at 17.28truept
\font\structmi cmmi10 at 17.28truept
\def\m{\ifmmode ^\bfm\else$^\bfm$\fi}
\def\bfm{{\setbox0\hbox{\bf I}\ifdim\ht0>9pt
\textstyle\normalbf m\else\bf m\fi}}