This is obviously gonna be a short instructable, but I wanted to make one because I have had an account on here for a while and havn't made any yet, sooo... yeah.
Step 1: How to Find Out
On their left hand, the thumb will be backwards. I see ebay items all the time titled "GI Joe?" so I thought this could be an easy first instructable. So all you have to do is take a look at THE ACTION FIGURE'Sleft hand. Not the hand on your left. If it has a backwards thumb, then it's most likely an authentic GI Joe.