A noble storm of hats is brewing...

Sale 1:

https://backpack.tf/item/7943315489

Sold for Dead Presidents Honcho's Headgear, but it can't be updated, excluding.

https://backpack.tf/profiles/76561198025795458#!/compare/1588118400/1588636800

https://backpack.tf/profiles/76561198025795458#!/compare/1588118400/1588636800

Marketplace Sales

https://marketplace.tf/items/tf2/137;5;u29

Sale 2:

https://backpack.tf/item/1391106258

Sold on Jun 15th for $31.99, Keys were $1.99 (16.08 Keys)

Taking 16 Keys (Rounding down)

Sale 3:

Sold on Mar 29th for $29.99, Keys were $1.69 (17.75 Keys)

Taking 18 Keys (Rounding up)

Credit to Xerg for the sale

Sale 4:

Sold on Jul 12th for $32.5, Keys were $1.98 (16.41 keys)

Taking 16 Keys (Rounding down)

And the following listing on https://mannco.store/item/14742 -

"for sale on mannco for $28/1.7 = 16, being sold by SexySparta so has probably been selling for a long time." - Xerg

Going with 16 flat, excluding 18 as it's older.

Original Suggestion: https://backpack.tf/suggestion/5f092dc5be402b12232b1ba4