Compare links:

51 keys + Aussie Stickybomb Launcher (~12) ----- credits to Dr Hotel Mario

https://backpack.tf/profiles/76561198087607344#!/compare/1521331200/1521504000

http://www.tf2outpost.com/trade/29394478 ----- caps at 61 keys

Bulk

https://backpack.tf/profiles/76561198405223769#!/compare/1516406400/1516492800

PE Katyusha (mini at 32) + MS Battin (mini at 6) + ~18 keys in sweets ----- 56 keys total

https://backpack.tf/profiles/76561198106233311#!/compare/1518393600/1518480000

https://backpack.tf/profiles/76561198156238574#!/compare/1518393600/1518480000

http://www.tf2outpost.com/trade/29539500 ----- B/O was 60

Katyusha sold with 6 keys for a GE Private Eye (40) here:

https://backpack.tf/profiles/76561198046580198#!/compare/1521504000/1521590400

https://backpack.tf/profiles/76561198106233311#!/compare/1521504000/1521590400

https://imgur.com/a/l83IE ----- sellers at 30 and 32 (young, but first one is the buyer from above), taking 30-34.

Battin' sold for 6 keys here (IDs match):

https://backpack.tf/profiles/76561198067679367#!/compare/1521158400/1521244800

https://backpack.tf/item/6001290150

https://imgur.com/a/0wvvM ----- 3 weeks unsold at 7, 6 is fine for this.