https://marketplace.tf/items/tf2/48;5;u8

Two sales:

$127.99 x2 = 73, 73 keys

https://backpack.tf/item/178493349 64 key buyout https://bot.tf/stats/listings/M0D3J6OE

https://backpack.tf/item/293502191 75 key buyout https://backpack.tf/item/293502191

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https://backpack.tf/profiles/76561198855485521#!/compare/1569110400/1569283200

https://backpack.tf/profiles/76561198192602363#!/compare/1568937600/1569024000

Untraceable, 80 keys went to the Burning Stovepipe

Buyout was 60 keys at the time

https://bot.tf/stats/listings/4OVLKJJV

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https://backpack.tf/profiles/76561198855485521#!/compare/1571184000/1571270400

https://backpack.tf/profiles/76561198044684270#!/compare/1571184000/1571270400

31 keys? quicksell price.

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https://backpack.tf/profiles/76561198183396245#!/compare/1567209600/1567296000

https://backpack.tf/profiles/76561197993987295#!/compare/1567036800/1567296000

Bulk

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https://backpack.tf/profiles/76561198331167728#!/compare/1572307200/1572393600

https://backpack.tf/profiles/76561197993987295#!/compare/1572048000/1572393600

Seems to be Circling Hearts Mining Light + 6 keys + Corona Australis (14 keys)

Buyout was 64 keys https://bot.tf/stats/listings/4OVXO35V

Hearts Mining Light updating to ~45 keys https://backpack.tf/suggestion/5dc65169d381720680221045

This will cap at the 64 key buyout.

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https://backpack.tf/profiles/76561198331167728#!/compare/1572566400/1572739200

https://backpack.tf/profiles/76561198280357510#!/compare/1572652800/1572739200

Seems to be bulk for keys

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https://backpack.tf/profiles/76561198280357510#!/compare/1572912000/1572998400

https://backpack.tf/profiles/76561197993182335#!/compare/1572912000/1572998400

65 keys

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Sales:

64 (MP buyout cap)

64 (hearts mining + 20)

65 (pure keys)

73 (MP)

73 seems to be an outlier.

Thank you K1ng.

Going with 64-65.