In general, a proof card is a "test" card a company creates to compare and evaluate designs, photos, cardstock, new technology, colors, and overall appearances. True proof cards are not created for release to the general public, but are intended to be used "in-house" by the card manufacturer itself. Some proof cards will have blank backs containing no printing, while others may have blank fronts. Other proofs may have only one or two colors on the fronts of the cards, as companies used these "progressive proofs" to check for color imbalances. Proofs are sometimes printed on thinner card stock than the actual issue, or may even have several layers of acetate plastic, each containing one color, that lay upon each other to give the appearance of a regular card.

Most proof collectors seem to be interested in examples from 1991 and earlier, since the methods used to produce cards began to change dramatically around that time. Companies now use computers to produce the cards, which has taken away the need for the old style color-separation proof sets.

In August of 1989, Topps teamed with the world famous Guernsey's auction house to hold one of the most celebrated auctions in trading card history. Topps opened up its' legendary vault and made available vintage proof cards, uncut proof sheets, and other unique items that were unobtainable to collectors up until that time. To this day, you will find proof cards for sale on the internet that found their way into the hobby thanks to the '89 Topps auction. Many of these items still include the letters issued by Topps/Guernsey's when they were originally sold. Today, the internet door for proof cards is wide open. Topps is once again offering proofs directly from its' vault -- this time with the help of a steady stream of Ebay auctions.

Proof cards from companies other than Topps can be found here and there, but a collector must educate himself on the differences between an authentic proof card and a regular card that is being sold as a proof for inflated prices. One old trick is to take a regular uncut sheet of cards, cut the sheet into panels of two to nine cards, and call them "proof sheets." This can turn a common $15 uncut sheet into several hundred dollars of profit for unscrupulous sellers. Another trick is to find a blank backed card, taken straight from a retail pack, and call it a proof card. Many "coin" or circle shaped cards are also released in uncut sheet form, allowing dishonest sellers to cut these cards off the sheets in square patterns, and call them proofs (after all, they are square shaped, right?) Yet another trick is to photocopy a regular card in black and white, and try to represent the card as a special uncolored proof. The bottom line is collectors need to know the provenance of the proof cards they are buying. Some proof cards are no different -- front or back -- than regularly issued cards, so provenance and/or letters of authenticity are paramount for those cards.

Some of the most desirable, rarest, and expensive proof cards in existence are "unissued proofs." These are proof cards that were created for consideration in a set, but were changed before the actual product was issued (assuming the product was issued at all). An unissued proof card may show a player as a member of his former team, while the actual issued card shows him in his new uniform. Probably the most famous of all unissued proof cards is the 1977 Topps Reggie Jackson, which pictures Reggie in an Orioles uniform. The cards that were issued in packs have a different photo that shows him in an airbrushed Yankees uniform. Keith Olbermann owns two of these unissued proofs, with one of them selling at auction in 2004 for over $6,000! Other types of unissued proofs may show different photos (even though the teams remain the same), variations in border colors, and occasionally players who were bumped from the set altogether because of space considerations.

In the mid '90s, some companies began to create "printer's proof" type insert cards that were randomly placed into unopened packs. As you now know, these cards are not proofs at all, but were created for the sole purpose of retail sale.