I am a big fan of trading in TF2 and I have seen people report that some items in the game are duped, which considerably lowers the price of the item. Thus, I want to be able to know how to tell if an item is duped. Is there any easy way to find out?
The only "easy way" is to check an item's history on www.tf2items.com or www.tf2outpost.com if you use that site. After that it involves tedious backpack checking to see if the new owner has the item and if other people who owned the item still have copies of the same exact item (which is why you check the history). If the new owner has the same copy of an item previous owners still have, then most likely that item has been duped. Duped items are seen mostly in unusual trades. I would look at this: http://wiki.teamfortress.com/wiki/Community_trading_tips, as it can prevent you from getting scammed and buying duped items.