The last mail-away figure to be advertised on Empire Strikes Back figure cards was Admiral Ackbar. Admiral Ackbar was the sneak preview figure for the new Star Wars movie Revenge of the Jedi. The title later changed to Return of the Jedi. This offer required 6 proofs of purchase and expired January 31st, 1983. This one again came with a flyer describing the role the character would play in the movie. Here is how the offer appeared on the back of figure cards.
Here is mine with the mailer box and paperwork. There does exist a version where the paperwork has the Return of the Jedi title and they are much harder to find than the Revenge.
Finally the commercial advertising the offer.