Cold Metal

https://backpack.tf/item/6104550707

Sale 1) Sold for a Max's Severed Head (18.85 Keys at the time) + Mannrobics (1.15 Keys)

https://backpack.tf/profiles/76561198141443255#!/compare/1510876800/1510963200

18.85 + 1.15 = 20 Keys

https://backpack.tf/item/3346034459

Sale 2) Sold for a Kill-a-Watt Bootleg Base Metal Billycock (8.5 Keys) + Aces High Copper's Hard Top (8 Keys) + ~3 Keys of Items + 2 Keys

https://backpack.tf/profiles/76561198040154461#!/compare/1514332800/1514592000

8.5 + 8 + 3 + 2 = 21.5, which rounds to 22 Keys

Billycock Mini

https://backpack.tf/profiles/76561198284891268#!/compare/1512604800/1512691200 - Sold for 8 Keys + 5 Refined

https://backpack.tf/profiles/76561198040154461#!/compare/1515024000/1515110400 - Sold + Aces High Copper's Hard Top for a Cloud 9 Familiar Fez

There's no Mini for the Fez, so I'll use its old price of 17 Keys (it's hardly outdated). Taking 8 Keys for the Copper's as shown below.

Copper's Hard Top Mini

https://backpack.tf/profiles/76561198121830870#!/compare/1509408000/1509494400 - Sold for 8 Keys + 13 Refined

https://backpack.tf/profiles/76561198310990013#!/compare/1509494400/1509667200 - Buyer's Backpack for the above sale.

https://backpack.tf/profiles/76561198166763414#!/compare/1512864000/1512950400 - Sold for 8 Keys + 8.11 Refined

In the first sale, the Flame Thrower in the Buyer's Backpack was sold for Keys. 8 of the Keys (+ 13 Refined) were sold for the Copper.