Time Warp Big Chief (41 - 43)
https://backpack.tf/stats/Unusual/Big%20Chief/Tradable/Craftable/70

Sale 1)
https://backpack.tf/item/4536451887 + https://marketplace.tf/items/tf2/309;5;u70;strange - Sold for $45 via Buy order to MISTA (Who's known for buying low via Mp.tf)

Sale 2)
https://backpack.tf/item/4536451887 + https://marketplace.tf/items/tf2/309;5;u70;strange - Sold for $79.99 / $1.84 = 43 Keys

Sale 3)
https://backpack.tf/item/4536451887 + https://marketplace.tf/items/tf2/309;5;u70;strange - Sold for $40.47, low, probably via Mastikhor's buy order

Sale 4)
https://backpack.tf/item/4536451887 + https://marketplace.tf/items/tf2/309;5;u70;strange - Sold for $74.88 / $1.82 = 41 Keys

Summary:
41 and 43