https://backpack.tf/profiles/76561198056898423#!/compare/1687910400/1690934400 - Only 17 Refined match

https://gladiator.tf/time-machine?item=Severed+Serration+Fat+Man%27s+Field+Cap&at=2023-07-28T16%3A34%3A00.000Z - Likely ~34

https://backpack.tf/profiles/76561199072654974#!/compare/1692835200/1692921600 - 35 Keys

https://imgur.com/a/vTuXjUo - Confirmation of the 35 Key sale

https://gladiator.tf/time-machine?item=Severed+Serration+Fat+Man%27s+Field+Cap&at=2023-08-24T13%3A20%3A00.000Z - It was listed for 35

https://backpack.tf/profiles/76561198069143099#!/compare/1693353600/1693440000 - Purple Energy Throttlehead (28.5 Keys) + 20 Keys

https://imgur.com/a/jcjHjXF

Throttlehead Sales:

https://backpack.tf/profiles/76561198140316312#!/compare/1697673600/1697760000 - Bulk sale

https://backpack.tf/profiles/76561198314640429#!/compare/1695427200/1695513600 - Only 7 Keys appear

https://backpack.tf/profiles/76561199183171982#!/compare/1692144000/1692230400 - Bulk sale

https://backpack.tf/profiles/76561199183171982#!/compare/1692230400/1692316800 - ?

https://backpack.tf/profiles/76561199101376092#!/compare/1697673600/1697760000 - ?

https://backpack.tf/profiles/76561198160981552#!/compare/1688428800/1688515200 - ?

https://backpack.tf/profiles/76561198160981552#!/compare/1688947200/1691539200 - ?

https://backpack.tf/profiles/76561199032721186#!/compare/1689292800/1689552000 - ?

https://backpack.tf/profiles/76561199277135317#!/compare/1690156800/1691712000 - ?

https://backpack.tf/profiles/76561199388511269#!/compare/1690156800/1690243200 - ?

https://backpack.tf/profiles/76561198283091524#!/compare/1690502400/1690761600 - 29 Keys

https://backpack.tf/profiles/76561198338602750#!/compare/1685750400/1695772800 - ?

https://marketplace.tf/items/tf2/31282;5;u10 - Sales at 28 to 29 Keys

With the 35 Key sale being listed at or below 37 Keys for a month, and there being a second likely sale at 34, that'd suggest 60 is too high.

35 to 49 would work as a range for this.