I still got some questions:
1. Item ID/Original ID: are these IDs given by the game or websites like tf2items.com?
2. If both IDs are the same, but the only owner of the item purchased it by trading, doesn't it mean the item is duped, too? (no "..item still exists..." shows up, nor the former owner). I thought item IDs change when traded.
3. Do duped items count towards the total ammount of a certain item as shown on stats.tf?
4. When were the times when duping occured? I only know about arround July 2012, any other other timespans?
5. Has anyone heard that tf2wh.com was used massively for duping items? Why would anyone buy and sell valuable stuff there (still many are)?

Thank you

It could mean that the item isn't duped or that the possible duplicate is in a backpack that since hasn't been checked on tf2items.com, backpack.tf, etc.

"1. You shouldn't care if an item is duped." I understand this ;) I just wonder (and this is the reason for my post here) why you can read everywhere that this damn line "This item potentially still exists. Check the user's backpack to verify." VERFIES your item is duped.

Hi Champelliot, thx. For sure I tried to check these backpacks. But the items aren't any longer in their backpacks.

People say that if you can read the line "This item potentially still exists.
Check the user's backpack to verify." (when checking an item in your backpack via tf2items.com) you can be sure that the item is duped.

Can someone tell me if that true to a 100% IN ANY CASE or not?

Because I had tf2items.com saying this line for items from that I know that they are definitely not duped. Here's why: I bought an item (110% not duped, just not possibel) with an alt. account without ckecking the backpack of this alt. account with tf2items.com. Then I traded this item to my main account, checked my main accounts backpack with this site and could read the line "...potentially still exists..". After then checking my alt. account with tf2items.com the line wasn't any longer there.

If I own an item, but am NOT THE LAST OWNER, then I can be sure it is duped, that's clear. But when I am the last owner, can't I be sure the item is not duped? Regardless tf2items saying "This item potentially still exists. Check the user's backpack to verify."?

Thx in advance.