\newbox\unterscbox
\newdimen\unterscw
\font\untersca=untersca at 72.27truept
\setbox\unterscbox=\vbox{\hbox{%
\untersca\char0\char1\char2}}
\unterscw=\wd\unterscbox
\setbox\unterscbox=\hbox{\vbox{\hsize=\unterscw
\parskip=0pt\offinterlineskip\parindent0pt
\hbox{\untersca\char0\char1\char2}}}
\ifx\parbox\undefined
    \def\setuntersc{\box\unterscbox}
\else
    \def\setuntersc{\parbox{\wd\unterscbox}{\box\unterscbox}}
\fi
