%%% Suffer from suffix

% When a font is defined, TeX scans but ignores a filename extension.
% A side effect of that is that the code below works to select
% texnansi-lmr10.tfm

\font\test=texnansi-lmr10.WhoToldYouToUseASuffix?
\test oeps

% And depending on whether your local Web2c version is compiled with
% or without multiple file extensions support, so may this:

\font\test=texnansi-lmr10.4pt.
\test oeps

\end
