Although “pack searching” is not illegal, it is considered unethical by many people who collect trading cards, especially sports cards. It is, however, a widespread practice, particularly at retail department stores like Meijer, Walmart and Target. Hobby shop owners and trade show vendors likely will ask you to leave their stores or booths if they see you pack searching. “Jersey cards” are prime targets of pack searches. They contain a card with a patch of a game-worn jersey from a player and make an individual pack of cards thicker, heavier or stiffer (and more valuable).
Flex a pack of cards gently between your fingers. Jersey cards are thicker and more rigid than a common card. The pack will not bend as easily as a normal pack. (Card companies, of course, are aware of all the tricks of the trade and randomly insert “dummy” cards into packs.)
Weigh the pack. Seasoned veterans can do this by touch alone. Others actually use portable scales, which they tote into stores and use while they pick through displays of cards. Some people buy cards by the box, take them home, weigh the individual packs, remove the packs they deem worthy and re-sell the common packs.
Measure the thickness of the pack. Again, experienced collectors do this by feel. If a jersey card is present, the thickness of the entire pack will be greater than a normal pack. Some collectors take it a step further and manipulate the cards within the pack, searching for a single card that appears thicker (this sometimes is referred to as the “slide” test). Dummy cards offer some safeguards, but they are not included in all packs and, thus, the odds are in the pack searcher’s favor if he buys a seemingly thicker pack.
Use calipers to measure a pack’s thickness. This is a more scientific approach to the thickness-feel test and provides incredibly accurate results. Some people have no compunction at all about performing this test in-store. Others buy boxes of cards and take them home to test for thickness. They keep the packs that show promise and sell the others. Dishonest hobby shop owners and dealers have been known to employ this practice.
Press down on the middle of a pack. This often is called the “swipe” test. A jersey pack will present an indentation or seem more spongy than a regular pack
If you’re new to collecting, get to know the hobby. Sports card collecting can be cutthroat and you need to know what you’re doing or risk getting fleeced by underhanded dealers.
Hobby stores have suffered from unscrupulous dealers who will remove potential jersey packs from boxes and replace them with common packs. Beware of such practices. Develop a relationship with a trusted dealer and don’t haphazardly patronize unknown dealers. If you buy packs of cards at a retail store, check the packs’ wrappers. People are not below opening or cutting the packs to peek inside. Avoid suspicious or damaged packs.