Sale #1:

https://backpack.tf/item/10670329962

https://backpack.tf/profiles/76561199581722058#!/compare/1764892800/1764979200 ~ no matches

https://backpack.tf/profiles/76561199533260966#!/compare/1764806400/1764892800 ~ only 1 key leaves

Sale #2:

https://backpack.tf/profiles/76561198073818313#!/compare/1763078400/1763164800 ~ 2 scrap matches

https://backpack.tf/profiles/76561199581722058#!/compare/1763078400/1763164800

Sale #3:

https://backpack.tf/profiles/76561199026390261#!/compare/1762992000/1763078400 ~ no matches

https://backpack.tf/profiles/76561198073818313#!/compare/1762992000/1763078400 ~ 51 keys leave, 29 of these match

Sale #4:

https://backpack.tf/profiles/76561198849024279#!/compare/1762041600/1762214400 ~ 43 keys + 1 scrap match

https://backpack.tf/profiles/76561199026390261#!/compare/1761955200/1762041600

Sale #5:

https://backpack.tf/profiles/76561198120643050#!/compare/1761955200/1762041600

https://backpack.tf/profiles/76561198849024279#!/compare/1761955200/1762041600 ~ added 34 keys for a Fully Charged Blast Defense

If we took sellers of the blast defence (90), it would put this below buyers.

Sale #6:

https://backpack.tf/item/4210000916

https://backpack.tf/profiles/76561199026390261#!/compare/1769299200/1769385600 ~ 66 keys match

https://backpack.tf/profiles/76561198035547951#!/compare/1768953600/1769299200

https://ibb.co/359HpPjh ~ 66 keys + 24 ref

Sale #7:

https://backpack.tf/profiles/76561199830130823#!/compare/1767916800/1768780800 ~ dump/cashout/scam?

https://backpack.tf/profiles/76561199026390261#!/compare/1768694400/1768780800

Buyers at 60

Sales @ 43, 51(?), <57, 66

Taking 66.