Rack Pipe

https://backpack.tf/item/798810007

Sale 1) Bulk sale

https://backpack.tf/profiles/76561198086948995#!/compare/1539129600/1539216000

Sale 2) ?

https://backpack.tf/profiles/76561198232697088#!/compare/1540598400/1540684800 - Seller's Backpack

https://backpack.tf/profiles/76561198353908023#!/compare/1540598400/1540684800 - Buyer's Backpack

Sale 3) Sold for 35 Keys + ~1 Key of Items

https://backpack.tf/profiles/76561198353908023#!/compare/1541030400/1541462400

35 + 1 = 36 Keys

https://backpack.tf/item/854446147

Sale 4) Sold for 23 Keys + 4 Refined

https://backpack.tf/profiles/76561198081270783#!/compare/1540857600/1540944000

Sale 5) Sold for 36 Keys

https://backpack.tf/profiles/76561197961309499#!/compare/1543190400/1543276800

https://backpack.tf/item/1454005746

Sale 6) Sold for 38 Keys

https://backpack.tf/profiles/76561198312583107#!/compare/1538611200/1538697600

Sale 7) ?

https://backpack.tf/profiles/76561198160628764#!/compare/1538697600/1538956800

Sale 8) Bulk sale with the DBD Kabuto

https://backpack.tf/profiles/76561198080179568#!/compare/1539129600/1539216000

https://backpack.tf/profiles/76561198061926111#!/compare/1538352000/1539216000

https://marketplace.tf/items/339;5;u35 - Sold for $85 (high), $50 (low), $69 when Keys were ~$1.65 each, and $70 when Keys were ~$1.81 each

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

69 / 1.65 = 41.82, which rounds to 42 Keys

70 / 1.81 = 38.67, which rounds to 39 Keys