It's stamped right on the 10 pack from Wilkinson Sword. 'Gota be 16 or older, bub! Now I don't know about you guys, but I was younger than 16 when I first looked in a mirror and asked myself: "Wait, I'm getting a beard and mustache? At MY age!? What IS this crap!?"
Curiously, the 5 pack doesn't display the same markings.