/usr/share/man/man1/gfscompare3D.1.gz is in gerris 20110329-dfsg.2-1build2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/gfscompare2D.1.gz
/usr/share/man/man1/gfscompare2D.1.gz