1979: KRYPTONITE ROCKS AD

From July 1979 get yer authentic chunks of KRYPTONITE: 

Yes!  I'm a pal of ol' Supes so I can think of no better way of extending the hand of friendship than keeping a small quantity of the one thing that can harm him sitting on my shelf.  Foolproof marketing guys!

I love that they have tried to explain it all away with a completely improbable ruse ("in no way to be confused with actual fact") that this is somehow being helpful.  Sure, sure. 

Safe and non-toxic... unless you are the Man of Steel.

This appeared in US comics in 1979.