Resuggestion, thanks to K1ng for the info!

Sale 1:

https://backpack.tf/profiles/76561198164651434#!/compare/1533772800/1533945600

https://backpack.tf/profiles/76561198053547683#!/compare/1533859200/1534032000

Untrace.

Sale 2:

https://backpack.tf/profiles/76561198053547683#!/compare/1534032000/1534118400

https://backpack.tf/profiles/76561198069493147#!/compare/1534032000/1534118400

Sold for HG Mullet(17)

Sale 3:

https://backpack.tf/profiles/76561198069493147#!/compare/1534032000/1534118400

https://backpack.tf/profiles/76561198349207524#!/compare/1534118400/1534204800

Sold for CPS Ze Goggles

Goggles Mini:

https://backpack.tf/suggestion/5bafc24ccf6c7524b21ac3d5

Suggestion for 13.5 keys

Sale 4:

https://backpack.tf/profiles/76561198349207524#!/compare/1534204800/1534291200

https://backpack.tf/profiles/76561198182957762#!/compare/1534204800/1534291200

Sold with negligible sweets for Smoking Tree

Tree Mini:

https://backpack.tf/suggestion/5baf2a8dcf6c7541fb19775b

Suggestion for 15 keys

Sale 5:

https://backpack.tf/profiles/76561198385940902#!/compare/1534291200/1534377600

https://backpack.tf/profiles/76561198049149130#!/compare/1533600000/1534377600

Bulk.

Sale 6:

https://backpack.tf/profiles/76561198049149130#!/compare/1535673600/1535760000

https://backpack.tf/profiles/76561198111376629#!/compare/1535068800/1535846400

Untrace.

Sale 7:

https://backpack.tf/profiles/76561198111376629#!/compare/1536192000/1537228800

https://backpack.tf/profiles/76561197961168134#!/compare/1536105600/1536192000

Untrace.

Sale 8:

https://backpack.tf/profiles/76561197961168134#!/compare/1536192000/1536278400

https://backpack.tf/profiles/76561198275783474#!/compare/1536105600/1536278400

Sold for 11 keys

Sale 9:

https://backpack.tf/profiles/76561198275783474#!/compare/1536278400/1536451200

https://backpack.tf/profiles/76561198198986799#!/compare/1536364800/1536451200

Untrace.

Sale 10:

https://backpack.tf/profiles/76561198198986799#!/compare/1536451200/1536537600

Sold for Steaming Toy Soldier + negligible sweets

Use there.

Sale 11:

https://backpack.tf/profiles/76561198135388328#!/compare/1536796800/1536883200

https://backpack.tf/profiles/76561198021055079#!/compare/1536796800/1536883200

Bulk.

Total sales @:

11, 13.5, 15, 17 keys

K1ng's Part:

4 keys were added with the Mullet in sale 2

https://backpack.tf/profiles/76561198069493147#!/compare/1534032000/1534118400 ----- use near ID here.

Given the unsold at 18, that sale will be an outlier. Resuggest at 14-15.

Taking 14 - 15 keys