If you are on a debian based distrobution, you can use the package manager to figure it out:
$ dpkg -S $(which man)
man-db: /usr/bin/man
This tells us man-db is the package which owns /usr/bin/man.
$ dpkg -l man-db
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-=================================
ii man-db 2.10.2-1 amd64 tools for reading manual pages
Then we ask what version of man-db is installed. This is man-db's upstream version 2.10.2 released by the distribution with an extra -1. The -1 represents a patch done by the distribution. This may just include build-rules, but could also include fixes to 2.10.2 ported from later versions.