I love seeing monsters and elements of the fantastique used in advertising. This one is rather an odd but pleasantly cheeky promotion for Benylin. Must have been a monsterkid on their marketing team that came up with this one 😉 And to think, this was #1 in a series!
From seller phxsunny's listing: "Here is a very rare Mailer Advertisement promotion by Parke Davis for Benylin Medicine in the 1980's. The ad promotion was called "How to treat a monster" and these Monstrous Mailers were sent with a Benylin Monster wind up Toy (which still works) and probably a bottle of Benylin. (No Benylin comes with this auction) Only for the products shown."