The profile used to install the site is stored in the variable `install_profile`. There's a few different ways you can see the value:

  - Pop into the `variable` table in your database and search for `install_profile`:
        
        select value from variable where name='install_profile';
  - Install the Devel module and visit `example.com/devel/variable`
  - Put this custom code in a template file somewhere: 

        <?php print variable_get('install_profile', 'No install profile found.'); ?>

Hope that helps