Snapper

https://backpack.tf/item/933929639

Sale 1) Sold + 12 Keys for a Blizzardy Storm Napper's Respite

https://backpack.tf/profiles/76561198083643512#!/compare/1536796800/1536883200 - Seller's Backpack

https://backpack.tf/profiles/76561198091502579#!/compare/1536710400/1536796800 - Buyer's Backpack

Will be used there.

Sale 2) Sold for $29.99 when Keys were ~$1.73 each

https://marketplace.tf/items/248;5;u35

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

29.99 / 1.73 = 17.33, which rounds to 17 Keys

https://backpack.tf/item/1535485956

Sale 3) ?

https://backpack.tf/profiles/76561198185631051#!/compare/1538697600/1538870400

Sale 4) Bulk sale for a Blizzardy Storm Dr's Dapper Topper

https://backpack.tf/profiles/76561198142892266#!/compare/1538870400/1538956800

Sale 5) Sold for ? Keys

https://backpack.tf/profiles/76561198064608021#!/compare/1539648000/1539734400

Sale 6) Sold for 15 Keys

https://backpack.tf/profiles/76561198159855421#!/compare/1542412800/1542499200

https://backpack.tf/item/6425347222

Sale 7) Sold for 15 Keys + 11 Refined

https://backpack.tf/profiles/76561198344933095#!/compare/1538179200/1538352000

Rounds to 15 Keys

https://backpack.tf/item/6803115410 - Nothing traceable

https://marketplace.tf/items/248;5;u35 - Sold for $17.65 (low), $32.69 when Keys were ~$1.76 each, $25 (~$1.77 each), and $29.99 (~$1.73 each)

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

32.69 / 1.76 = 18.57, which rounds to 19 Keys

25 / 1.77 = 14.12, which rounds to 14 Keys

29.99 / 1.73 = 17.34, which rounds to 17 Keys

Since 19 was the oldest and furthest from the other sales, I'll call that high.