Oh, what the hell. I'll take a whack at it.
I'm pretty sure that one was Chesterfield cigarettes. I remember that 100-millimeter cigarettes had begun to appear on the market and Chesterfield, probably just trying to find a way to differentiate itself from its competitors, decided to market a 101-millimeter cigarette, that was "just a silly millimeter longer."
Silly it was, because the difference in length was almost imperceptible (one millimeter is about 4/100ths of an inch), but it made for a neat advertising slogan.
OK, let's see if anyone remembers this one from the 70s:
He likes it! Hey, Mikey!
