Sale 1:

https://backpack.tf/profiles/76561198166749360#!/compare/1588118400/1588896000

https://backpack.tf/profiles/76561198085142983#!/compare/1588550400/1588636800

Untrace

sale 2:

https://backpack.tf/profiles/76561198085142983#!/compare/1588636800/1588723200

https://backpack.tf/profiles/76561198131081286#!/compare/1588636800/1588723200

Sold with 8 keys for Bubbling Fragger(19)

Total is 11 keys

sale 3:

https://backpack.tf/profiles/76561198131081286#!/compare/1588723200/1588809600

https://backpack.tf/profiles/76561198095713164#!/compare/1588032000/1588723200

Sold for TW Pot(12.5)

sale 4:

https://backpack.tf/profiles/76561198095713164#!/compare/1588032000/1588723200

https://backpack.tf/profiles/76561198956707902#!/compare/1588636800/1588723200

https://ibb.co/174VRwt (thanks to Ghost for the info!)

Sold for Bubbling Fragger(19) + 1 key

Total is 20 keys

Sale 5:

https://backpack.tf/profiles/76561198956707902#!/compare/1588809600/1589241600

https://backpack.tf/profiles/76561198311431152#!/compare/1589155200/1589241600

Sold for Vivid Scrap(22)

Sale 6:

https://backpack.tf/profiles/76561198311431152#!/compare/1590624000/1590969600

https://backpack.tf/profiles/76561198114402400#!/compare/1590883200/1590969600

Bulk

sale 7:

https://backpack.tf/profiles/76561198956707902#!/compare/1589500800/1589587200

https://backpack.tf/profiles/76561198033378852#!/compare/1589500800/1589587200

Sold with DayDream Sterling for spells

sale 8:

https://backpack.tf/profiles/76561198033378852#!/compare/1589587200/1589760000

https://backpack.tf/profiles/76561198257203147#!/compare/1589673600/1589760000

https://backpack.tf/profiles/76561197995983788#!/compare/1589673600/1589760000

Untrace / bulk

sale 9:

https://backpack.tf/profiles/76561197995983788#!/compare/1589760000/1589846400

https://backpack.tf/profiles/76561198203885895#!/compare/1589587200/1589846400

Sold for Miami Noble

Noble Mini:

https://backpack.tf/suggestion/5f1b5000bb010731a3118d28

Suggestion for 16 keys

sale 10:

https://backpack.tf/profiles/76561198203885895#!/compare/1589587200/1589846400

https://backpack.tf/profiles/76561198122522362#!/compare/1589760000/1589846400

Sold for Steaming Brain Bowl + 4 keys

Bowl Mini:

https://backpack.tf/suggestion/5f1b56c8bea25c553a14a9fb

Suggestion for 15 keys

Total is 19 keys

sale 11:

https://marketplace.tf/items/tf2/31008;5;u133

$18.1 / $1.82 = 9.95 keys

$22.22 / $1.89 = 11.76 keys

$22.22 / $1.90 = 11.69 keys

Total sales @:

10, 11, 12, 12, 13, 16, 19, 20, 22 keys

https://i.imgur.com/7BEUPOO.jpg

2 month unsold for 15 keys,

buyers up to 7 keys,

given unsold,

and that 22 resold in bulk where it was valued for much lower,

let's try 11 - 19 keys, conserving at seller.