We can know the CRM version, roll up and service pack by checking the version number of CRM.
The first digit indicates the application version(CRM 5 – 2011, 6 – 2013, 7 – 2015)
The second digit indicates the service pack level.
The third digit indicates the update rollup.
So the above image is from an organization on RTM 2013 update rollup 2
This image is from organization RTM CRM 2015 with out any rollups.