Sale 1: ~27 Keys.

Sold For Dead Presidents Company Man (15.5) + Strange Specialized Killstreak Flame Thrower (Field-Tested) (9) + 2 Keys = 26.5 keys.

https://backpack.tf/profiles/76561198219263116#!/compare/1552608000/1552953600

https://backpack.tf/suggestion/5cf74f9bd381724589347c42

Strange Specialized Killstreak Flame Thrower (Field-Tested) Mini:

~9 Keys.

Sold For Bill's Hat (2.45) + Non-Craftable Flip-Flops (5.2) + Tour of Duty Ticket (0.48) + Non-Craftable Festivizer (0.9) + 5 ref in items = 9 Keys.

https://backpack.tf/profiles/76561198219263116#!/compare/1553212800/1553385600

https://backpack.tf/profiles/76561198167772727#!/compare/1553212800/1553385600

Sale 2: ~22 Keys Pure.

https://backpack.tf/profiles/76561198113402108#!/compare/1552694400/1552780800

https://backpack.tf/profiles/76561197982127154#!/compare/1552694400/1552780800

Sale 3: ~20 Keys Pure. (QS)

https://backpack.tf/profiles/76561197982127154#!/compare/1552780800/1552867200

https://backpack.tf/profiles/76561198240055810#!/compare/1549497600/1552867200

Sale 4: Untrace.

https://backpack.tf/profiles/76561198240055810#!/compare/1552867200/1553040000

https://backpack.tf/profiles/76561198068709170#!/compare/1552867200/1553040000

Sale 5: Gambled?

https://backpack.tf/profiles/76561198068709170#!/compare/1552780800/1552867200

https://backpack.tf/profiles/76561198016663834#!/compare/1552780800/1552867200

Sale 6: ~24 Keys Pure.

https://backpack.tf/profiles/76561198077247195#!/compare/1554681600/1554854400

Sale 7: ~28 Keys Pure.

https://backpack.tf/profiles/76561198125791160#!/compare/1559174400/1559260800

https://backpack.tf/profiles/76561198038472306#!/compare/1559174400/1559260800

https://marketplace.tf/items/30743;5;u34

Sale 8: Low.

Mar 29

$28.92 / $1.79 = 16.16 keys

Including Sales: 22/24/27

3 Months unsold at 27 keys - https://imgur.com/zMn58L6 - https://backpack.tf/item/4450146135

Buyers at above 21 keys.

Going with 22-27 keys.

Thanks to scourge for the premium and all the help!