Challenge 19, Team F.L.A.M.B.E.S!

6th suggestion, made by Mikey!

Marketplace Sales:

https://marketplace.tf/items/tf2/1172;5;u3015

1:

Unable to find item history.

May 10th - $98.77

Keys were $1.90 that day, so 98.77 / 1.9 = 51.98 keys, rounding to 52.

Sale 2:

Unable to find item history.

May 25th - $70.22 - Quicksell / below buy orders.

Sale 3:

Unable to find item history.

May 29th - $73.01 - Quicksell / below buy orders.

Sale 4:

https://backpack.tf/item/5201170765

June 10th - $99.99

Keys were $2.01 that day, so 99.99 / 2.01 = 49.75 keys, rounding to 50.

Other Sales:

5:

https://backpack.tf/profiles/76561198205939253#!/compare/1586822400/1586908800

https://backpack.tf/profiles/76561198031743044#!/compare/1586822400/1586908800

Bulk

Summary of Valid Sales:

1 @ 52

1 @ 50

Taking 50-52 keys.