/usr/lib/x86_64-linux-gnu/libgrafX11.so is in libgrafx11-1-dev 20061220+dfsg3-4.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libgrafX11.so.1_gfortran.2006
/usr/lib/x86_64-linux-gnu/libgrafX11.so.1_gfortran.2006