Sale 1: sold for 30 keys pure

(The IDs of the keys match the taunt)

https://backpack.tf/item/6342747367

https://backpack.tf/profiles/76561198928421771#!/compare/1592179200/1592265600

https://backpack.tf/profiles/76561198109149008#!/compare/1592179200/1592265600

Sale 2: Sale on Marketplace.tf, the item going to the buyer's inventory

https://backpack.tf/item/7964804583

Marketplace.tf sales: https://marketplace.tf/items/tf2/1172;5;u3027

(Untraceable) May 31 2020: $59 (median key price: $1.91, 30.89 keys) ~31 keys

(Sale 2) July 30 2020: $150 (median key price: $1.92, 78.13 keys) ~78 keys

There's an unsold at 35 keys with 2 sales in the 30-31 keys range, 78 keys is an outlier

With the proof I have, going with 30-31 keys