Buying game-worn jerseys can be tricky but learning about what to look for to make sure what you're getting is authentic can also be a lot of fun.
It can involve some research, like hunting down actual photos of games from the season the jersey was worn to see if it matches. Sometimes you can even photo match to a specific game when the jersey was worn. Getty Images is one excellent resource for photo matching a jersey that is being sold as having been worn in a game. Hunting down photos can involve some effort, but it's also a kind of like an archaeological expedition. When and if you can actually match your jersey to a photo, it's also a great piece of authentication you'll want to keep.
The first major difference to be aware of is that 'game issued' doesn't mean game 'used'. A game-issued jersey might look just like the one www.Cowboysnflofficialstore.com Derek Jeter wore on the field, but it might have just sat in his locker or a storage locker somewhere. When an item is described as 'game issued', figure it never saw action and bid accordingly if you're interested at all. You'll often see "GI" next to a jersey description and that's what it means.
Other abbreviations include: NNOB (no name on back, often found on college jerseys or older jerseys. Generally that means there never was a name or number on the back. NOBR means "name on back removed", meaning the jersey may have had a name at Womens Jay Ratliff Jersey some point but it was taken off and passed down to a player at the next level down the organizational chain.
Some game worn jerseys have "game wear" especially hockey jerseys and this is a great selling point. You'll see rips and repairs, especially on older jerseys. While newer jerseys sometimes also come with repair (again, especially hockey jerseys), it's less common since jerseys are changed so often. "Team repairs" are seen as a positive.
Scuff marks on hockey jerseys, typically black in color, come from the tape used on sticks. Some jerseys in all sports have blood or sweat stains. Many organizations don't wash their game-used jerseys to please collectors who want to see the actual wear, tear and work that they sustained while in game action. It's sometimes a smelly job, but there's no authentication like photo-matched sweat!
Tagging is ultra important. If the seller is willing to answer specific questions about whether the jersey has proper tagging on the inside, chances are he's already researched it. The tag contains the manufacturer name and logo, sometimes the year of issue and the size of the jersey.
Knowing the size jersey a player wears and his preference, if any, for alterations, can be a big help when buying a jersey but players do change sizes as they get older. Players who are traded don't always get the right sized jersey when first arriving with their new club.