I have a stack of these left over from childhood. Actually, I think these were my sister's. I will be listing more, after I see how the two up now do. They have to be about 40 years old.
I was collecting these, and sticking them on everything (my notebooks, binders, in my locker etc) starting in 1975! They may have come into the market just a tad before that date, but yes these are collector items FOR SURE! :-D