Derpingson
Totally Ordinary Human
thats the FAMOUS scorching merryweather, and no, its impossible it has 4 copies unless you found all of them in each others BP's.
I clicked one of the tf2b.com links you provided, went on the guy's Steam profile, ran it through tf2items.com, clicked on the hat, and sure enough it said that it might still exist in the user's backpack four times. Went in and checked myself, in their backpacks that is.
The item: http://www.tf2items.com/item/766804303
When I view the backpack who's unusual have been marked as "This item potentially still exists.", and I click on level 42 merryweather, it comes back to the link above.