bot.tf:

https://bot.tf/stats/item?def=1107&q=5&ef=%2772&craft=1&aus=0&ks=0

https://i.imgur.com/qBPrxrB.png

Sold past 90 days

1 @ 4 keys, 20.00 ref --> 4.4 keys

1 @ 4 keys, 20.00 ref --> 4.4 keys

1 @ 5 keys --> 5.00 keys

1 @ 5 keys --> 5.00 keys

Bought past 90 days

1 @ 4 keys --> 4.00 keys

1 @ 4 keys --> 4.00 keys

1 @ 4 keys, 2.22 ref --> 4.00 keys

Marketplace:

https://marketplace.tf/items/tf2/1107;5;u3004

{not proof} Currently 1@ $14 (7.6 keys) and 1@ $15 (8.15 keys)

Confirmed marketplace sales:

Jun 10: 1 @ $7.95 / 2.01 = 4 keys

Jul 30: 1 @ $11.77 / 1.92 = 6.1 keys

Aug 2: 1 @ $11.50 / 1.90 = 6.1 keys

History sales:

Sale 1

https://backpack.tf/profiles/76561198885258799#!/compare/1594080000/1596672000

https://backpack.tf/profiles/76561198453530349#!/compare/1596585600/1596672000

untrace

Sale 2:

https://backpack.tf/profiles/76561199070255861#!/compare/1596758400/1596844800

https://backpack.tf/profiles/76561198992823032#!/compare/1596758400/1596844800

bulk sale

Sale 3:

https://backpack.tf/profiles/76561198153874080#!/compare/1596758400/1596844800

https://backpack.tf/profiles/76561198992823032#!/compare/1596758400/1596844800

bulk sale

Sale 4:

https://backpack.tf/profiles/76561198153874080#!/compare/1596844800/1597017600

https://backpack.tf/profiles/76561198097747485#!/compare/1596931200/1597017600

bulk sale

Sale 5:

https://backpack.tf/profiles/76561198358296372#!/compare/1594857600/1594944000

https://backpack.tf/profiles/76561198448501306#!/compare/1594857600/1594944000

untrace

Summary: 4-6.1 keys fits best