Thanks Blaze for another free suggestion! And also to Wrein again for passing it up

Atomic Captain Space Mann

https://backpack.tf/stats/Unusual/Captain%20Space%20Mann/Tradable/Craftable/92

https://marketplace.tf/items/tf2/30646;5;u92

https://backpack.tf/item/4242638125 - sold for $689 (363 keys), $350 (184 keys)

https://backpack.tf/profiles/76561198074625962#!/compare/1591315200/1591401600

https://backpack.tf/profiles/76561198286257338#!/compare/1591228800/1591401600 - sold with 230 keys for Strange Green Energy Bonk Boy (was used there)

https://backpack.tf/profiles/76561198050509345#!/compare/1591315200/1591401600

https://backpack.tf/profiles/76561198074625962#!/compare/1591315200/1591401600 - sold for Strange Haunted Ghosts Bonk Boy (182.5) = 183 keys

https://backpack.tf/profiles/76561198066369838#!/compare/1589846400/1589932800

https://backpack.tf/profiles/76561198251704884#!/compare/1589846400/1589932800 - sold with Frozen Icefall Universal Translator for Frozen Icefall Hunter in Darkness (being used there)

https://backpack.tf/profiles/76561198080179568#!/compare/1588809600/1588896000

https://backpack.tf/profiles/76561198066369838#!/compare/1588809600/1588896000

https://bot.tf/stats/listings/M19W5ZO1 - sold for Sunbeams Large Luchadore (outdated but buyers at 158) + Harvest Moon Fat Man's Field Cap = 220 keys b/o easily

https://backpack.tf/profiles/76561198044095472#!/compare/1590278400/1590537600

https://backpack.tf/profiles/76561198084367252#!/compare/1590364800/1590537600 - unsure

https://backpack.tf/profiles/76561198251704884#!/compare/1591056000/1591142400

https://backpack.tf/profiles/76561198050509345#!/compare/1591056000/1591142400

https://bot.tf/stats/listings/MQ0L0VLP - sold for Arcana Engineer's Cap (?) + stuff

Arcana Engineer's Cap

https://backpack.tf/stats/Unusual/Engineer's%20Cap/Tradable/Craftable/73

https://backpack.tf/profiles/76561198251704884#!/compare/1594857600/1594944000

https://backpack.tf/profiles/76561198105071091#!/compare/1594771200/1594944000 - unsure

https://backpack.tf/profiles/76561198118157202#!/compare/1590105600/1590192000

https://backpack.tf/profiles/76561198050509345#!/compare/1590105600/1590192000 - sold for Morning Glory Texas Ten Gallon (165) + 13 keys = 178 keys (low, doubt this was the whole sale)

no possible mini for Arcana Engineer's Cap, will need confirmation of sales

Conclusion:

sales at 183, 184, 220, 363

185 - 220 keys (rounded)