Fireworks

https://backpack.tf/item/4299065542

Sale 1) Sold for a Stormy 13th Hour Burning Bandana + Morning Glory Industrial Festivizer (52.5 Keys) + Kill-a-Watt Scout Shako

https://backpack.tf/profiles/76561198071230830#!/compare/1557273600/1557360000

The Burning Bandana has no Mini.

Sale 2) Sold for a Bonzo-the-All-Gnawing Engineer's Cap

https://backpack.tf/profiles/76561198090147535#!/compare/1561334400/1561420800

https://backpack.tf/profiles/76561198123389475#!/compare/1561334400/1561420800

This can be used to update the Engineer's Cap.

https://backpack.tf/item/4282470575

Sale 3) Bulk sale for an Arcana Rotation Sensation

https://backpack.tf/profiles/76561198066404955#!/compare/1554768000/1554854400

Sale 4) Bulk sale for a Golden Frying Pan

https://backpack.tf/profiles/76561198134512931#!/compare/1555372800/1555459200

Sale 5) Sold + Australium Force-a-Nature (9.5 Keys) for a Miami Nights Antlers (252.5 Keys)

https://backpack.tf/profiles/76561198040280241#!/compare/1555286400/1555459200

252.5 - 9.5 = 243, which I'll round to 245 Keys

Antlers Mini

https://backpack.tf/suggestion/5d1ea6a1d3817277fb5990fa - 252.5 Keys

Sale 6) Bulk sale for a Bonzo-the-All-Gnawing Cotton Head

https://backpack.tf/profiles/76561198297554259#!/compare/1556323200/1556409600

https://marketplace.tf/items/tf2/30623;5;u80 - Sold for $515.20 when Keys were ~$1.83 each

https://marketplace.tf/items/tf2/5021;6

515.20 / 1.83 = 281.5, which I'll round to 280 Keys