Item 1: https://backpack.tf/item/16470358731

Sale 1:

https://backpack.tf/profiles/76561198088878793#!/compare/1772496000/1772582400

https://backpack.tf/profiles/76561199142817642#!/compare/1772496000/1772582400

Bulk

Sale 2:

https://backpack.tf/profiles/76561199142817642#!/compare/1775433600/1775520000

https://backpack.tf/profiles/76561198396756155#!/compare/1775001600/1775520000

Looks like Bulk?

Sale 3:

https://backpack.tf/profiles/76561198396756155#!/compare/1775520000/1775606400

https://backpack.tf/profiles/76561199564942025#!/compare/1775433600/1775520000

Bulk Dumped to STN for ??

Item 4 & Item 5:

https://backpack.tf/item/3703279068

https://backpack.tf/item/273148516

Sale 4 & 5:

https://marketplace.tf/items/tf2/135;5;u19

Sold on MP for $37.75 on the 16th of March and 13th of May

Keys were:

16th of March 1.9 = 19.8 (Rounding up to 20 keys)

13th of May 1.98 = 19.06 (Rounding down to 19 keys)

//

Sellers:

BPTF - https://imgur.com/a/mDRNKdM - 3 @ 22 keys, 1 @ 25 keys, 1 listed on mp (~27.7 keys)

MPTF - https://marketplace.tf/items/tf2/135;5;u19 - 1 @ $37.75, 1 @ $49.99

STN - https://stntrading.eu/item/tf2/Unusual+Circling+Heart+Towering+Pillar+of+Hats - 1 @ 18 keys and 33.44 ref

SCM - https://steamcommunity.com/market/listings/440/Unusual%20Towering%20Pillar%20of%20Hats?appid=440&q=Circling%2520Heart - None

Sale(s):

19, 20

Even though there is a seller at around 18.6 keys it would still round up to 19. Additionally this sole seller at 19 I don't believe should invalidate the 20 sale either especially since its legit only 1 key difference. Including both into range, going with 19 - 20 keys