Here is what I tried so far:

\documentclass{article} \usepackage[USenglish,ngerman]{babel}%%% The main language is German \usepackage{tabularx} \usepackage{lipsum} \usepackage{calc} \usepackage{hhline} \pagestyle{empty} \begin{document} \lipsum[1]\\ \noindent% ====\textsf{TII3}\leaders\hbox{=}\hfill\foreignlanguage{USenglish}{timed}====\strut\\ \begin{tabular}{@{}|p{\textwidth-1.35em}|@{}} % \hhline{|=|}\\[-2.6ex]%%% Well, we need some text inside the double ruler. \begin{tabular}{@{}l@{\ \ }l@{}l@{\ }l@{}} \textsf{\textbf{in}} &\(z'\)&\(\colon\)&\textsf{T3}\\ \textsf{\textbf{out}} &\(z\)&\(\colon\)&\textsf{T3} \end{tabular}\\ \hline\\[-2.2ex] \(\bar{z} = \bar{z'}\)\\ \hline \end{tabular}\\\\ \lipsum[2] \end{document}

And here is the result:

1. Any idea how to typeset the header

╒═══TII3════...════timed═══╕

using a double ruler in the style of hhline, i.e., such that it attaches to the vertical lines of the table, and such that it doesn't look as if it were typed on a 1950's typewriter? Of course, one can use {xe|lua}latex and Unicode box drawings characters, but it would not work with pdflatex, and one would have to use a monospace alphabet and drop tabular anyway.

2. Any idea how to get rid of the ad-hoc width 1.35 em of the rulers and replace it by something automatically computed?

Thx in advance.