Bear with me, for this is slightly confusing, unless you are into Star Wars.
Star Wars cards are actually split into many series, but for many collectors it comes down to "The Originals", which are the films released first in 1977 (!Star Wars", 1980 ("The Empire Strikes Back" and 1981 ("The Return of the Jedi") and the later films which had different actors. Confusingly the second three films dealt with a time before the originals took place, and then the third three carried on the tale after the originals were over.
These stickers were for the second original film, "The Empire Strikes Back", and there were three series issued. Luckily the sticker borders are in different colours, so we can tell them apart, series one being yellow, series two blue, and series three green.
They were not long sets, series one and two being of thirty-three cards, and series three being just twenty-two. All had alphabet letters, but the first two series had twenty-two of these, in a variety of combinations, then there were eleven stickers shaped as characters from the film. Whilst our set was just the twenty two letter stickers, and no characters.
The packets were twenty-five cents each. And they contained bubble gum, so we are still amongst the trade cards rather than the commercial. The stickers and the cards were placed inside the packets at a ratio of "12 Movie Photo Cards, I sticker, 1 stick bubble gum".
The stickers were slightly more popular with younger collectors, who used them for the purpose for which they were intended, by removing the sticker, fixing it to something they believed it would enhance, and throwing the back away. Therefore the stickers, today, are scarcer.
Now twhilst looking at some other Star Wars cards I have discovered that this set does actually appear in our vintage British Trade Index part III - where it is described as :
Initial Stickers - The Empire Strikes Back (A). 89 x 64. Back with sectional picture. Front inscribed "Lucas, Ltd. (LFL) 1980. All Rights Reserved". Nd. 67/88 (22) As same numbers in set TO6-8 in RB.30
That RB.30 is our original Australian and New Zealand Index, and this entry, TO6-8, is for the cards, which are catalogued as :
The Empire Strikes Back. 89 x 64. Nd. (132). Nos. 131/132 inscribed "Topps Presents - Star Wars - The Empire Strikes Back", other numbers anonymous. Issued in U.S.A.