The last offer to appear on cards were for the mail-away coins. The stickers for the offer were actually applied by the retailers and not at the factory. Basically for one proof of purchase, the sticker for the offer cut off the card, and your receipt got you a free coin in the mail. There were 62 total coins that you could receive. Some of the coins are very common and others are very scarce. Gus Lopez of the Star Wars Collectors Archive created a catagory system based on rarity of the coins. In 1985 The Power of the Force line was released and the coins were available on cards. The original plan was for all 62 coins to be available on cards, but only about half of them made it before the Star Wars toy line was cancelled, so that last half of the coins can get very pricey. People who actually wrote into Kenner requesting a set were offered one for $29. This was never advertised so only a few people took advantage of this. Complete sets are now selling in the $5000 range. I currently have 18 left to go for my set. Here are some sample of the offer. First is a Return of the Jedi figure with the sticker advertising the mail in promotion, then a Power of the Force figure with the coin on the card, and then the back of the card making me want to collect all 62.
Here are my coins in the frame my dad and I built last summer.
A few collectors have memory of a commercial for the coins, but unfortunately it has not ever surfaced at this point in time. Hopefully someone out there will find it on an old VHS tape one of these days.
Finally here is a picture of what I would consider a Holy Grail of mine. This is the executive sets that were given to the high ups at Kenner and Lucasfilm. They are framed and included two sets of the coins showing front and back. There are said to be 10 of these sets that were created.