Aye, I Eye

https://backpack.tf/item/423870939

Sale 1) ?

https://backpack.tf/profiles/76561198861630295#!/compare/1566604800/1566950400

https://backpack.tf/profiles/76561198159312241#!/compare/1567209600/1567296000

https://backpack.tf/item/301492875

Sale 2) Bulk sale for a Scorching Flames Patriot Peak

https://backpack.tf/profiles/76561198129596771#!/compare/1561680000/1561852800

Sale 3) Bulk sale for a Scorching Flames Shellmet

https://backpack.tf/profiles/76561198348844757#!/compare/1561939200/1562284800

Sale 4) Marketplace

https://backpack.tf/profiles/76561198043936328#!/compare/1561939200/1562025600

https://backpack.tf/profiles/76561198086259875#!/compare/1562889600/1562976000

Sale 5) Sold for 22 Keys

https://backpack.tf/profiles/76561198003188332#!/compare/1566518400/1566604800

https://backpack.tf/profiles/76561198083529516#!/compare/1566518400/1566604800

https://backpack.tf/item/276434804

Sale 6) Sold for 18 Keys

https://backpack.tf/profiles/76561198080179568#!/compare/1560988800/1561075200

Sale 7) Sold for 19 Keys

https://backpack.tf/profiles/76561198042708321#!/compare/1561248000/1561680000

https://backpack.tf/profiles/76561198135116208#!/compare/1560988800/1562198400

IDs match.

https://marketplace.tf/items/tf2/47;5;u16 - Sold for $42.99 when Keys were ~$1.82 each and $36 when Keys were ~$1.84 each

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

42.99 / 1.82 = 23.62, which rounds to 24 Keys

36 / 1.84 = 19.57, which rounds to 20 Keys