I forgot that Burger Chef had ESB posters as well as ANH posters;

Burger Chef Empire Strikes Back posters

These posters were apparently originally not meant to be used by Burger Chef at all.
According to artist Boris Vallejo;
"The posters were actually done originally as a promotional campaign for the Coca Cola Company, to be given away at movie theaters that showed “The Empire Strikes Back”. Subsequently they found other avenues."
Source

(I’m guessing that the fourth poster was made for this, but Burger Chef only used the first three, hence there’s no “Number four of four” or anything similar written on it. Either that or it could have been used to promote the other three posters. Does anyone actually know what this fourth poster was used for?)