Burning bright.

https://backpack.tf/item/4701975411

Sale 1) Sold for a Green Black Hole Head Warmer (75 Keys)

https://backpack.tf/profiles/76561198192602363#!/compare/1505865600/1505952000

Using the 75 Key price because this sale happened 4 days after the Head Warmer was priced.

Sale 2) Sold for a Sulphurous Prince Tavish's Crown + Massed Flies Tyrant's Helm + 6 Keys + ~1 Key of Items

https://backpack.tf/profiles/76561198173442901#!/compare/1508112000/1508198400

http://www.tf2outpost.com/trade/29378751 - Capped by the Buyout of 75 Keys

Sale 3) Sold for a Duped Burning Flames Professional's Panama (66 Keys)

https://backpack.tf/profiles/76561198240745690#!/compare/1509926400/1510012800

The Panama was priced with Duped sales.

Sale 4) Sold + Terror-Watt Hat With No Name + 3 Keys for a Duped Purple Energy Swagman's Swatter + Steaming Villain's Veil

https://backpack.tf/profiles/76561198151572595#!/compare/1511395200/1511654400 - Seller's Backpack

https://backpack.tf/profiles/76561198085628805#!/compare/1511568000/1511654400 - Buyer's Backpack

Bulk sale.

Sale 5) Sold for a Strange Starstorm Insomnia Federal Casemaker (67.5 Keys) + 10 Keys

https://backpack.tf/profiles/76561198085628805#!/compare/1511654400/1511740800

67.5 + 10 = 77.5, which rounds to 78 Keys

Casemaker Mini

https://backpack.tf/suggestion/5a2d44bdcf6c7514a84ac6e6 - 67.5 Keys

Sale 6) Sold + Green Confetti Salty Dog for a Magnetic Hat Protector Captain Space Mann (110 Keys) + 19 Keys

https://backpack.tf/profiles/76561198163204583#!/compare/1512086400/1512172800 - Seller's Backpack

https://backpack.tf/profiles/76561198087172601#!/compare/1512086400/1512172800 - Buyer's Backpack

http://www.tf2outpost.com/trade/29458560 - Capped by the Buyout of 75 Keys

Salty Mini

https://imgur.com/a/UXrEJ - 4 Month Unsold at 50 Keys

Sale 7) Sold for a Haunted Ghosts Trophy Belt (49.5 Keys) + Bubbling Winter Woodsman (20 Keys) + 3 Keys

https://backpack.tf/profiles/76561198087172601#!/compare/1512345600/1512432000

49.5 + 20 + 3 = 72.5, which rounds to 73 Keys

Trophy Mini

https://backpack.tf/suggestion/5a2c0ad344325a5ddf0754b4 - 49.5 Keys

Woodsman Mini

https://backpack.tf/profiles/76561198036445124#!/compare/1511740800/1511827200 - Sold for 20 Keys

https://imgur.com/a/P6bZD - CAaronD said the Woodsman was sold for 20 Keys.

https://backpack.tf/item/6141807197

Sale 8) Sold for a Purple Energy Surgeon's Stahlhelm

https://backpack.tf/profiles/76561198062073519#!/compare/1505692800/1506470400

The only Mini on the Stahlhelm that I could find is for a Duped Secret Engineer's Cap, which has no Mini.

http://www.tf2outpost.com/trade/28370499 - 1 Year Seller at 68 Keys (Probably not at 68 for the full time, as it wasn't mentioned in previous suggestions)

https://imgur.com/a/ZlP4l - Using the Seller at 60 Keys with the Seller at 68 Keys above to rule 78 Keys a high Outlier.