Including 56 Keys.

https://backpack.tf/item/1666246214

Sale 1) Sold for 45 Keys

https://backpack.tf/profiles/76561198119428262#!/compare/1527552000/1527638400

Sale 2) ?

https://backpack.tf/profiles/76561198253093948#!/compare/1532476800/1532563200

Sale 3) Sold for a Scorching Flames Commando Elite (46.5 Keys) + 5 Keys

https://backpack.tf/profiles/76561198251043990#!/compare/1533686400/1533859200

46.5 + 5 = 51.5, which rounds to 52 Keys

Commando Mini

https://backpack.tf/suggestion/5b6c172c44325a291b3ae327 - 46.5 Keys

https://marketplace.tf/items/30038;5;u69 - Sold for $62.24 (low), $80 when Keys were ~$1.94 each, and $109.99 when Keys were ~$1.96 each

80 / 1.94 = 41.23, which rounds to 41 Keys

109.99 / 1.96 = 56.11, which rounds to 56 Keys

Counting 41 as low.