United States Presidents have been a popular subject with candy-related trading card producers, since they are a subject that is sure to gain parental approval. This particular card set from the pre-World War II era is especially famous among card collectors... or is it infamous?
The card fronts feature a tinted portrait or photo of an American President, against a red, blue, or orange background, surrounded by a thin white border. The President's name is superimposed in white lettering over his head, while a colored bar at the bottom bears the title, 'American Heroes Caramel.' The card backs repeat the President's name, plus a subtitle, then his numerical rank (i.e., 'Twenty-fifth President') and a block of biographical text. The bottom of the card back gives the number of cards in the set as well as an ad stating that a full set of 31 Presidential cards can be mailed to the company for one pound of chocolate, plus the return of the cards.
Well, that appears to have happened only twice since 1934; U.S. Caramel cheated the kids of America by making sure they could never collect a full set. The card for William McKinley has only been found twice, and each of these copies has the word CANCELLED stamped across the back (as well as the words CANDY PAID on one of them), along with oddly-shaped holes punched in the cards so that they could not be redeemed for chocolate again. (Two sets of cancelled cards are known to exist, and both have been auctioned for around $10,000.) This, of course, was to make sure that kids would keep buying the candy to obtain the cards, in the hopes of obtaining a pounf of chocolate at some point in the future.
Another way that U.S. Caramel may have cheated their buyers was with the use of the colored backgrounds on the card fronts: each card (besides McKinley) can be found in each of the three background colors of red, blue, and orange. This may or may not have been done to entice kids to collect every President in every color variation - as some modern collectors do - but it's possible.
Note: The scarcity involved has made the U.S. Caramels McKinley card one of the rarest, and most desirable, in the card collecting hobby. In any case, the 30-card set, not including the McKinley, is considered to be complete.
The American Card Catalog number for this set is R114.