"Nobody" showing up in permissions

Nobody is an automatic system assignment to files that have no known owner. By default the nobody user is read only. This can occur when migrating data from an older version of OS X where the newer version's permissions, users, and groups have changed. It can also happen when transferring files from another operating system that does not implement file permissions in the same way or not at all.

In the example you provided only users in the admin and staff groups can read or write the file.

This, in the Terminal app, lists all groups by name:

*dscacheutil -q group |grep name:*

For more details, use:

*dscacheutil -q group*

and for users, use:

*dscacheutil -q user |grep name:*

or

*dscacheutil -q user*

Most of those are OS users and groups, so don't try mucking with them.