Sale 1:

https://backpack.tf/profiles/76561198125791160#!/compare/1533081600/1533168000

https://backpack.tf/profiles/76561198294542813#!/compare/1531526400/1533168000

Untrace (maybe the 15?)

Sale 2:

https://backpack.tf/profiles/76561198080669489#!/compare/1529712000/1529798400

https://backpack.tf/profiles/76561198080253443#!/compare/1529712000/1529798400

Untrace.

Sale 3:

https://backpack.tf/profiles/76561198123631904#!/compare/1530576000/1530662400

https://backpack.tf/profiles/76561198219200107#!/compare/1530576000/1530662400

Bulk?

Sale 4:

https://backpack.tf/profiles/76561198219200107#!/compare/1530662400/1530748800

https://backpack.tf/profiles/76561198144945119#!/compare/1528761600/1530748800

Untrace.

Sale 5:

https://backpack.tf/profiles/76561198144945119#!/compare/1530748800/1531180800

https://backpack.tf/profiles/76561198030343929#!/compare/1530662400/1530748800

Untrace.

Sale 6:

https://backpack.tf/profiles/76561198030343929#!/compare/1531008000/1531094400

https://backpack.tf/profiles/76561198799075257#!/compare/1530230400/1531094400

Sold for Smoking Yellow Belt(17.5)

Sale 7:

https://backpack.tf/profiles/76561198799075257#!/compare/1531094400/1531180800

https://backpack.tf/profiles/76561198168993666#!/compare/1530835200/1531180800

Keys, untrace.

Sale 8:

https://backpack.tf/profiles/76561198126724119#!/compare/1531526400/1532131200

Untrace.

Sale 9:

https://backpack.tf/profiles/76561198126724119#!/compare/1532217600/1532563200

https://backpack.tf/profiles/76561198268140274#!/compare/1532476800/1532563200

Sold with 3 keys for Mallard Doctor Sack

Use there.

Sale 10:

https://backpack.tf/profiles/76561198268140274#!/compare/1532476800/1532563200

https://backpack.tf/profiles/76561198097073455#!/compare/1532476800/1532563200

Sold for CPS Samur-Eye(20)

Sale 11:

https://backpack.tf/profiles/76561198097073455#!/compare/1532476800/1532563200

https://backpack.tf/profiles/76561198180662462#!/compare/1532476800/1532563200

Sold with ~1.4 keys in sweets for 12 keys

Total is ~11 keys.

Sale 12:

https://backpack.tf/profiles/76561198170440245#!/compare/1531785600/1531872000

https://backpack.tf/profiles/76561198032016356#!/compare/1531699200/1531785600

Untrace, maybe bulk?

Sale 13:

https://backpack.tf/profiles/76561198032016356#!/compare/1531699200/1531785600

https://backpack.tf/profiles/76561198268050117#!/compare/1531785600/1531872000

Sold for 11 keys

Sale 14:

https://backpack.tf/profiles/76561198268050117#!/compare/1531699200/1531785600

https://backpack.tf/profiles/76561198836867687#!/compare/1531699200/1531785600

Sold for 12 keys + negligible ref

Sale 15:

https://backpack.tf/profiles/76561198836867687#!/compare/1531699200/1531785600

https://backpack.tf/profiles/76561198149175706#!/compare/1531699200/1531785600

Sold for 12 keys..

Sale 16:

https://backpack.tf/profiles/76561198149175706#!/compare/1531872000/1531958400

https://backpack.tf/profiles/76561198069558815#!/compare/1531526400/1531958400

Sold for Atomic Translator(18.5)

http://www.tf2outpost.com/trade/29716332

B/O of 14 keys, capping.

Sale 17:

https://backpack.tf/profiles/76561198069558815#!/compare/1532131200/1533686400

Sold for OF Fruit Shoot

Use there.

Sale 18:

https://backpack.tf/profiles/76561198092295228#!/compare/1532131200/1532390400

https://backpack.tf/profiles/76561198109452231#!/compare/1532131200/1532217600

Untrace.

Sale 19:

https://backpack.tf/profiles/76561198109452231#!/compare/1532390400/1532563200

https://backpack.tf/profiles/76561198121373648#!/compare/1531353600/1532649600

SCM sale?

Sale 20:

https://backpack.tf/profiles/76561198177105083#!/compare/1531958400/1532044800

https://backpack.tf/profiles/76561197983219732#!/compare/1531958400/1532044800

Untrace.

Sale 21:

https://backpack.tf/profiles/76561197983219732#!/compare/1531958400/1532044800

https://backpack.tf/profiles/76561198011379022#!/compare/1531958400/1532044800

Sold for 11 keys, maybe more?

Sale 22:

https://backpack.tf/profiles/76561198011379022#!/compare/1532044800/1532217600

QS to bot

Sale 23:

https://backpack.tf/profiles/76561198847955284#!/compare/1533513600/1533600000

https://backpack.tf/profiles/76561198429029268#!/compare/1531958400/1533600000

Sold for 12 keys + 16.44 ref

Sale 24:

https://backpack.tf/profiles/76561198429029268#!/compare/1533600000/1533686400

Bulk.

Total sales @:

11(?), 11, 11, 12, 12, 12.5, 14, 17.5, 20 keys

https://i.imgur.com/jPYiMnz.png

Buyers up to 11.46 keys

Sellers down to 14, unsold at 17 for 3 months.

https://backpack.tf/item/5358933340 <-- unsold

https://backpack.tf/item/5362179992 <-- 14 seller

Let's go with 12 - 14 keys.