Choo Choo. Car 28.

Resuggestion, thanks to Randy for pointing out my error!

Sale 1:

https://backpack.tf/profiles/76561198337734785#!/compare/1531353600/1531440000

https://backpack.tf/profiles/76561198104134966#!/compare/1531353600/1531526400

Untrace.

Sale 2:

https://backpack.tf/profiles/76561198104134966#!/compare/1531872000/1531958400

https://backpack.tf/profiles/76561198116352227#!/compare/1530576000/1532217600

https://backpack.tf/profiles/76561198089253101#!/compare/1532044800/1532217600

Untrace.

Sale 3:

https://backpack.tf/profiles/76561198135388328#!/compare/1532217600/1532304000

https://backpack.tf/profiles/76561198353645984#!/compare/1532131200/1532304000

Sold for 22 keys (Really quick)

Sale 4:

https://backpack.tf/profiles/76561198828364444#!/compare/1532044800/1532131200

https://backpack.tf/profiles/76561198399762321#!/compare/1531267200/1532304000

Untrace.

Sale 5:

https://backpack.tf/profiles/76561198399762321#!/compare/1532304000/1533686400

https://backpack.tf/profiles/76561198011321852#!/compare/1532217600/1532304000

QS? Bp?

Sale 6:

https://backpack.tf/profiles/76561198135388328#!/compare/1534982400/1535068800

https://backpack.tf/profiles/76561198252999692#!/compare/1534550400/1535068800

Sold for 23 keys(ID match)

Sale 7:

https://backpack.tf/profiles/76561198252999692#!/compare/1535155200/1535241600

https://backpack.tf/profiles/76561198140316312#!/compare/1535068800/1535155200

Sold for 23 keys (2 used to buy Uncraft hat)

Sale 8:

https://backpack.tf/profiles/76561198140316312#!/compare/1535241600/1535328000

https://backpack.tf/profiles/76561198328478745#!/compare/1535155200/1535328000

Sold for 25 keys

Sale 9:

https://backpack.tf/profiles/76561198328478745#!/compare/1535155200/1535328000

https://backpack.tf/profiles/76561198152236177#!/compare/1535241600/1535328000

Untrace

https://backpack.tf/item/6584220184 <-- key was part of it

Sale 10:

https://backpack.tf/item/6584220184

https://backpack.tf/profiles/76561198081270783#!/compare/1535500800/1535587200

Sold for 17 keys + ~5 keys in ref

Total is ~22 keys

Sale 11:

https://backpack.tf/profiles/76561198260315279#!/compare/1530489600/1530748800

https://backpack.tf/profiles/76561198189001527#!/compare/1530230400/1530748800

Untrace.

Sale 12:

https://backpack.tf/profiles/76561198067775866#!/compare/1530230400/1530316800

https://backpack.tf/profiles/76561198828364444#!/compare/1530230400/1530316800

Sold for 28 keys

Sale 13:

https://backpack.tf/profiles/76561198086793593#!/compare/1529539200/1529625600

https://backpack.tf/profiles/76561198067775866#!/compare/1529539200/1529625600

Sold with ~4 keys in sweets for TW Riflemen

Riflemen Mini:

https://backpack.tf/suggestion/5b95c10d44325a301c0399ce

Suggestion for 36 keys

Total is 32 keys.

Sale 14:

https://backpack.tf/profiles/76561198076658566#!/compare/1529280000/1529539200

https://backpack.tf/profiles/76561198086793593#!/compare/1529366400/1529539200

Sold with ~5 keys in sweets for Blizzardy Danger

use there, looks high.

Sale 15:

https://backpack.tf/profiles/76561198189177226#!/compare/1517529600/1529020800

https://backpack.tf/profiles/76561198076658566#!/compare/1528934400/1529020800

Sold for DBD Armored Authority

AA Mini:

https://backpack.tf/suggestion/5b996e9acf6c757a096c6867

Suggestion for 25 keys.

Sale 16:

https://backpack.tf/profiles/76561198081270783#!/compare/1536969600/1537056000

Use there.

Total sales @:

22, 22, 23, 23, 25, 25, 28, 32

https://i.imgur.com/UmtC1uc.jpg

Buyers up to 21 keys

Sellers down to 29 keys

Considering 22 sold quick, as did 23,

Let's stick with 25 - 28 keys.