The trading card hobby puts a premium on proof cards. Proofs are pre-production test cards the printers use to check graphics and text before the final print run. Vintage card proofs are often blank backed, sometimes on different stock than the final cards, often with hand cut borders and little pencil written crosses on the borders. Proofs can sell for good money as they are rare and offer a look at the creation of the cards.
The collector should be aware that many cards resembling that proofs aren’t proofs. The manufacturers sometimes accidentally printed cards with blank backs and inserted them into the packs of gum or tobacco. These aren’t proofs, but printing errors.
There are also ‘cards’ that were long ago scissors cut from vintage advertising posters, tobacco albums and kids’ notebooks. As these cutouts have hand cut borders, blank backs and different than normal stocks, they are often mistakenly called proofs.
Collectors will also come across printer’s scraps, often of T206 baseball cards. These scraps came from a printer’s rejected sheet, often with poorly printed images, bad color registration and other graphics problems– which is why it was rejected, or scrapped, by the printer. These rejected sheets were rescued from the trash bin by workers, often to be taken home for the kids. The individual scrap cards that we see today were hand cut from the sheets. As the cards are hand cut, often oversized and usually with printing defects, they are often mistaken for proofs. As with the above mentioned blank backed cards, scraps are simply factory mistakes.
As you can see there are lots of non-proof cards that resemble proofs. When in doubt it’s best to bid on an unusual card assuming it isn’t a proof, because it likely isn’t. Scraps and other printing mistakes are collectable, but are much more plentiful and inexpensive than genuine proofs.