Sale 1:

https://backpack.tf/profiles/76561198183241050#!/compare/1566000000/1566604800

https://backpack.tf/profiles/76561198931070626#!/compare/1566000000/1566604800

Sold for 15 keys

sale 2:

https://backpack.tf/profiles/76561198109650171#!/compare/1569024000/1569110400

https://backpack.tf/profiles/76561198084367252#!/compare/1569024000/1569110400

Sold with 7 keys for Steaming Peak + negligible sweets

use there

Sale 3:

https://backpack.tf/profiles/76561198047648730#!/compare/1570060800/1570665600

https://backpack.tf/profiles/76561198337734785#!/compare/1570406400/1570492800

QS

sale 4:

https://backpack.tf/profiles/76561198337734785#!/compare/1570406400/1570492800

https://backpack.tf/profiles/76561198268922032#!/compare/1573171200/1573257600

Sold for 13 keys

sale 5:

https://backpack.tf/profiles/76561198299166370#!/compare/1566691200/1566777600

https://backpack.tf/profiles/76561198342161127#!/compare/1566604800/1566691200

QS

sale 6:

https://backpack.tf/profiles/76561198245906930#!/compare/1566691200/1567987200

https://backpack.tf/profiles/76561198080179568#!/compare/1567900800/1567987200

Sold for ~11 keys (QS)

Sale 7:

https://backpack.tf/profiles/76561198080179568#!/compare/1571097600/1571184000

https://backpack.tf/profiles/76561198151561701#!/compare/1571184000/1571270400

Sold for 14 keys

Sale 8:

https://backpack.tf/profiles/76561198151561701#!/compare/1571270400/1571616000

https://backpack.tf/profiles/76561198157613299#!/compare/1571184000/1571616000

Untrace

Sale 9:

https://backpack.tf/profiles/76561198342161127#!/compare/1566950400/1567036800

https://backpack.tf/profiles/76561198115069320#!/compare/1567036800/1567123200

sold for CTFL Defiant

use there

Sale 10:

https://backpack.tf/profiles/76561198115069320#!/compare/1567123200/1567382400

https://backpack.tf/profiles/76561198333986358#!/compare/1567036800/1567123200

Sold with 2 keys for TW Bot Dogger

Sale 11:

https://backpack.tf/profiles/76561198334598690#!/compare/1570838400/1570924800

https://backpack.tf/profiles/76561198197891710#!/compare/1570924800/1571270400

Sold for Stormy Private Eye(16.5)

Sale 12:

https://backpack.tf/profiles/76561198197891710#!/compare/1571270400/1571529600

https://backpack.tf/profiles/76561198080179568#!/compare/1571443200/1571529600

QS

sale 13:

https://backpack.tf/profiles/76561198080179568#!/compare/1572134400/1572220800

https://backpack.tf/profiles/76561198417131201#!/compare/1572048000/1572220800

https://backpack.tf/profiles/76561198417131201#!/compare/1572307200/1572393600

https://backpack.tf/profiles/76561198080179568#!/compare/1572220800/1572307200

tradeback

Sale 14:

https://backpack.tf/profiles/76561198203357988#!/compare/1569974400/1570147200

https://backpack.tf/profiles/76561198883670546#!/compare/1568937600/1570492800

SCM

Sale 15:

https://marketplace.tf/items/tf2/30001;5;u57

$27.99 / $1.79 = 15.64 keys

https://backpack.tf/item/2136667371

Total sales @:

11, 13, 14, 15, 15.64, 16.5 keys

buyers up to 9 keys,

2 month unsold at 14 keys,

cut off high and low end, conserve around the unsold,

taking 13 - 15 keys.