/usr/share/man/man3/gsm_implode.3.gz is in libgsm1-dev 1.0.13-4.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man3/gsm_explode.3.gz
/usr/share/man/man3/gsm_explode.3.gz