I just got the powercore+ 26800 and I was glad to see the authenticity check is on the box. it's a one time use code. if someone else used it before you they will let you know.
I don't think USA and UK have it though, anker seems to have only implemented that in countries where counterfeit products are rampant.
my friend took my old powercore 15600 and I realize how big of gap it left in my portable charging life. so I had to buy another.
anker make the best portable chargers hands down.