New sale:

https://backpack.tf/profiles/76561198341171690#!/compare/1595721600/1596067200

https://backpack.tf/profiles/76561198155926056#!/compare/1578528000/1596153600 - Can't deem what this is but it was listed at 15 keys - https://gyazo.com/9d6d0c3f6edc931089746b0bca034950

There's a seller on STN for 14 Keys 9 Ref - https://gyazo.com/77a0a6b8cde7db937b11fd3cdbcd51bd which has been there almost 2 months https://backpack.tf/item/8917898295

That wing mann doesn't support 11-18 also.

https://backpack.tf/profiles/76561198376072450#!/compare/1592956800/1593820800 - Sold for 8 keys

https://backpack.tf/item/8129473652 https://backpack.tf/profiles/76561198382658042#!/compare/1593043200/1593820800 - Sold for the spelled items

https://marketplace.tf/items/tf2/30809;5;u31 $20 = ~10 keys.

I would exclude 18 here based on the information above. You could try adding the buyer of the "15" sale but if in doubt I'd be happier with 11 flat.