That's too bad huh..

Sales

Sale 1: 18 keys~ here

https://backpack.tf/profiles/76561198002757046#!/compare/1598400000/1598486400

https://backpack.tf/profiles/76561198325273395#!/compare/1597881600/1598486400

https://bot.tf/stats/listings/4KV3R7D1

Sale 2: Untrace

https://backpack.tf/profiles/76561198440837262#!/compare/1597449600/1598313600

https://backpack.tf/profiles/76561198002757046#!/compare/1598227200/1598313600

Quickbuyer.

Sale 3: Untrace

https://backpack.tf/profiles/76561198035857135#!/compare/1590019200/1594252800

https://backpack.tf/profiles/76561198440837262#!/compare/1592697600/1597449600

Sale 4: Traced 0.33 ref lol

https://backpack.tf/profiles/76561198977523626#!/compare/1591833600/1591920000

https://backpack.tf/profiles/76561198267189538#!/compare/1591747200/1591833600

Quickbuyer.

Sale 5: Sold for Mega Strike Taunt: The Russian Arms Race (2.85 keys)+ 3 keys + prof ks capper (5.3 keys~)

https://backpack.tf/profiles/76561198330294613#!/compare/1598918400/1599091200

https://backpack.tf/profiles/76561199077192361#!/compare/1599004800/1599177600

It is likely more added, but those are the items that match in histories.

11 keys~

Sale 6: Untrace

https://backpack.tf/profiles/76561198410294713#!/compare/1598745600/1598832000

https://backpack.tf/profiles/76561198330294613#!/compare/1598745600/1598832000

Sale 7: Untrace

https://backpack.tf/profiles/76561199043177646#!/compare/1598745600/1598832000

https://backpack.tf/profiles/76561198410294713#!/compare/1597968000/1598745600

18~ was buyout

https://bot.tf/stats/listings/YD160ZJR

Sale 8: Untrace

https://backpack.tf/profiles/76561198196992211#!/compare/1597968000/1598054400

https://backpack.tf/profiles/76561199043177646#!/compare/1597968000/1598054400

Marketplace

https://marketplace.tf/items/tf2/465;5;u58

June

$33.99 on June 23 (33.99/2 = 17~)

https://manic.tf/keyprice/?at=2020-06-23

https://backpack.tf/item/2172637813

Classifieds

https://gyazo.com/5585699e5b7e8264d65b1b2898c69003

Summary

Sales at and 18. Unconfirmed buyout at 18.

Marketplace sales at 17.

Conclusion

Going with 17-18 here.