Pumice

https://backpack.tf/item/7956108269

Sale 1) Quicksold for 7 Keys + 4 Refined to a buy order

https://backpack.tf/profiles/76561198125151455#!/compare/1565913600/1566000000

https://backpack.tf/item/7957240659

Sale 2) Sold for 8 Keys

https://backpack.tf/profiles/76561198232026076#!/compare/1566000000/1566172800

https://backpack.tf/profiles/76561198120148073#!/compare/1565913600/1566000000

https://backpack.tf/item/2289856444

Sale 3) Sold for 9 Keys + 23 Refined

https://backpack.tf/profiles/76561198042938501#!/compare/1559433600/1559865600

Rounds to 9.5 Keys

Sale 4) Sold for 11 Keys

https://backpack.tf/profiles/76561198337734785#!/compare/1565827200/1565913600

https://backpack.tf/profiles/76561198400558905#!/compare/1565395200/1565913600

Sale 5) Sold + ~0.3 Keys of Items for an Aces High Your Worst Nightmare (8.5 Keys)

https://backpack.tf/profiles/76561198400558905#!/compare/1566086400/1566777600

8.5 - 0.3 = 8.2, which rounds to 8 Keys

Your Worst Nightmare Mini

https://backpack.tf/suggestion/5d69d9506780721be3136198 - 8.5 Keys

https://backpack.tf/item/7957047837

Sale 6) ?

https://backpack.tf/profiles/76561198830633436#!/compare/1566518400/1566604800

https://backpack.tf/profiles/76561198110011480#!/compare/1566518400/1566604800

Sale 7) ?

https://backpack.tf/profiles/76561198110011480#!/compare/1566604800/1566691200

https://backpack.tf/profiles/76561198129380689#!/compare/1566604800/1566691200

Sale 8) ?

https://backpack.tf/profiles/76561198129380689#!/compare/1566604800/1566691200

https://backpack.tf/profiles/76561198063803737#!/compare/1566604800/1566691200

Sale 9) ?

https://backpack.tf/profiles/76561198063803737#!/compare/1566691200/1566777600

https://backpack.tf/profiles/76561198110534225#!/compare/1566604800/1566777600

Sale 10) ?

https://backpack.tf/profiles/76561198110534225#!/compare/1566777600/1566864000

https://backpack.tf/profiles/76561198153536726#!/compare/1566777600/1566864000

Sale 11) Sold + 1 Key + ~0.25 Keys of Items for a Circling Peace Sign Crack Pot

https://backpack.tf/profiles/76561198153536726#!/compare/1566777600/1566864000

https://backpack.tf/profiles/76561198153525357#!/compare/1566777600/1566864000

Using for the Crack Pot.

https://marketplace.tf/items/tf2/30072;5;u59 - Sold for $21 when Keys were ~$1.85 each

https://marketplace.tf/items/tf2/5021;6

21/ 1.85 = 11.35, which rounds to 11 Keys

https://imgur.com/a/GenYOVg - 1 Day at 9 Keys, 1 Day Seller at 12 Keys, 2 Day Seller at 12 Keys, 3 Day Seller at 13 Keys, and a Buyer at 7.46 Keys

https://backpack.tf/item/7957047837

https://backpack.tf/item/7956108269

https://backpack.tf/item/2289856444

https://backpack.tf/item/7957240659

https://backpack.tf/u/76561198002757046