The message is a mystery

Believed to date from the 1980s, this appears to be a promotional picture of some kind, but the exact message has been lost.

We look for clues, but perhaps, at this distance in time, we look in vain. What hint can we take from the fact that the smaller Toblerone bar is proffered not as an entire item, as we might expect, but in a less than pristine state, as if the contents have already been partially consumed?

The secret is locked in time, and may even now have receded from living memory.
 
The past is another country, it has been said - not very cogently, because you can travel to another country, but not to the past.