After discussing with Shuffle, leaving 150 out is the best option.

A month later, buyer contacts. Better late, than never i guess. The aussies were actually involved, despite histories not matching.

Sale 1:

https://backpack.tf/item/2036261117

Sold for a Blizzardy Storm Mountebank's Masque (at the time was 75) + ~75 in aussies

150, buyout was 150: https://bot.tf/stats/listings/4EEVZJK2

https://backpack.tf/profiles/76561198236007746#!/compare/1575676800/1575936000

https://backpack.tf/profiles/76561198171107913#!/compare/1574553600/1576368000

Credits to frick:

https://gyazo.com/aced91e1cbc3c1727a6c8df2947f2156

https://gyazo.com/9e00963464c519f1ac575590b4c0ad95

https://gyazo.com/be827e9919bd613beef90ce3c48f16a5

Sale 2:

https://backpack.tf/item/2036261117

https://bot.tf/stats/listings/4W65P0KX (B/O of 120)

Sold for a Sunbeams Warhood (41.5, rounding up to 42, Keys), Blizzardy Tough Stuff Muffs (41.5 Keys, rounding to 42) & 20 Keys

Minis:

https://backpack.tf/suggestion/5dffa89d3b7a3f54ff27d819

https://backpack.tf/suggestion/5dffa87093b47f5c08758402

Taking 104 Keys

https://backpack.tf/profiles/76561198040585908#!/compare/1574812800/1574985600

https://backpack.tf/profiles/76561198236007746#!/compare/1574812800/1574985600

Sale 3:

https://backpack.tf/item/2036261117

Sold for 76 Keys Pure

https://backpack.tf/profiles/76561198060828964#!/compare/1574640000/1574726400

https://backpack.tf/profiles/76561198040585908#!/compare/1574640000/1574726400

Sale 4:

https://backpack.tf/item/2036261117

https://backpack.tf/profiles/76561198169939863#!/compare/1571961600/1572220800

https://backpack.tf/profiles/76561198060828964#!/compare/1571270400/1572134400

Bulk sale

Sale 5:

https://backpack.tf/profiles/76561198119658844#!/compare/1576800000/1577318400

https://backpack.tf/profiles/76561198171107913#!/compare/1577059200/1577145600

https://backpack.tf/item/2046967788

Iirc, thats his broker and this sale is collateral.

Sales: 150, 104 and 76. Cutting both ends, going with 105 flat.