first suggestion, here we go

Item History: https://backpack.tf/item/7427392770

I bought a Pro Ks version for 25 keys

Sale 1: https://backpack.tf/profiles/76561198167207112#!/compare/1555718400/1555891200

(Note: all the refined/cosmetics removed were turned into keys via scrap.tf, bp.tf just didn't get the chance to register them before the final trade was made)

Sale 2: (kind of) https://backpack.tf/profiles/76561198272011328#!/compare/1551744000/1552003200

(Might have been sold for a Stormy Storm Surgeon's Stalhelm and a Strange Coldsnap Coat (for a total of ~22 keys), but these might have been unrelated trades, as the the previous owner did not receive these items according to his backpack history; could be a discrepancy with backpack.tf)

Mini on Stalhelm: https://backpack.tf/stats/Unusual/Surgeon's%20Stahlhelm/Tradable/Craftable/29

Mini on Coldsnap Coat: https://backpack.tf/stats/Strange/Cold%20Snap%20Coat/Tradable/Craftable

There were at least 2 or 3 more sales in the item's history, but a few are between the same two people, so it's possible that one is an alt account. One owner traded the weapon away the same time they traded a few other expensive unusuals, so it's hard to know how much was paid for item in question.

This was my first suggestion, so any constructive criticism would be greatly appreciated!