Squad 3!

Sale 1:

https://backpack.tf/profiles/76561198332839477#!/compare/1553472000/1553558400

https://backpack.tf/profiles/76561198334712990#!/compare/1553472000/1553558400

= 15 keys + 47 refined metal

~ 16 keys

Sale 2:

https://backpack.tf/profiles/76561198334712990#!/compare/1552003200/1552176000

https://backpack.tf/profiles/76561198866419663#!/compare/1552176000/1552262400

Unclear (likely bought around buy order price)

Sale 3:

https://backpack.tf/profiles/76561198080179568#!/compare/1551052800/1551139200

https://backpack.tf/profiles/76561198866419663#!/compare/1551052800/1551139200

= 19 keys

Sale 4:

https://backpack.tf/profiles/76561198080179568#!/compare/1550880000/1550966400

(other side is unclear)

Unclear

Sale 5:

https://backpack.tf/profiles/76561198054760238#!/compare/1550880000/1550966400

(other side is unclear)

= B.M.O.C (4.63 keys)

~ 4.5 keys

Marketplace.tf sale:

https://marketplace.tf/items/303;5;u58/

= $30 / $1.81 (Feb 23)

= 16.57...

~ 17 keys

Notes:

- Sales not included here: https://backpack.tf/item/7082958791 involve the Helm being transfered between the user's bot and the user.

- 1 Seller at 16.5 keys (6 days old) https://imgur.com/a/J1tj7hG

Summary: 4.5, 16, 17, 19

Conclusion: Excluding 4.5, below buy orders. 16-19 keys.