You can use a browser plugin like firebug, or the dev tools to be able to view cookies for a given site. Depending on your implementation, you'll know which values to look for. In most modern cases; Go to the cookies tab and look for s_vi and s_fid and check their Domain. If that domain matches the domain for your site currently viewing, than it's a first party cookie being used.
I don't work for UnderArmour (I purposefully chose a different company), but I've attached a screenshot to show they are using First Part Cookies for SiteCat. They also use DTM to deploy with rules, and a version of Appmeasurement.
[img]UnderArmour-cookies.png[/img]
Good luck!