https://marketplace.tf/items/30658;5;u35

https://backpack.tf/item/7361436441 <-- Prolly Dec 17 sale

https://backpack.tf/item/6923206639 <-- Dec 27 or Dec 28 sale

Sales at 15, 20, 21

https://backpack.tf/profiles/76561198041108750#!/compare/1544486400/1544572800

17 keys

https://backpack.tf/profiles/76561198262258500#!/compare/1544572800/1544745600

Nothing matches

https://backpack.tf/profiles/76561198045730256#!/compare/1544313600/1544572800

16 keys, IDs match

https://backpack.tf/profiles/76561198337734785#!/compare/1545868800/1545955200

https://backpack.tf/profiles/76561198119149660#!/compare/1545868800/1545955200

Looks like nothing matches

https://backpack.tf/profiles/76561198203221120#!/compare/1541116800/1541203200

https://backpack.tf/profiles/76561198371168595#!/compare/1540684800/1541203200

Using there

Current sellers/buyers:

https://imgur.com/Wq5dOue

Sales we got:

15, 16, 17, 20, 21

Taking current sellers, I'd personally exclude 20 and 21 keys sales

15 looks rather quicksellish

16 and 17 sales left so that's our range

Woah, I almost forgot how to do these