Untraceable/Unusable sales:

https://backpack.tf/item/3199530498 - In and out of tf2mart

https://backpack.tf/item/5300103974 - all sales below

#1

Bought from scrap, untraceable

Seller: https://backpack.tf/profiles/76561198135388328#!/compare/1527379200/1527465600

Buyer: https://backpack.tf/profiles/76561197967578295#!/compare/1526947200/1527552000

#2

Sold to scrap, untraceable

Seller: https://backpack.tf/profiles/76561197967578295#!/compare/1527552000/1527724800

Buyer: https://backpack.tf/profiles/76561198135388328#!/compare/1527552000/1527638400

#3

Bought from scrap, untraceable

Seller: https://backpack.tf/profiles/76561198135388328#!/compare/1528848000/1528934400

Buyer: https://backpack.tf/profiles/76561198052906308#!/compare/1528761600/1528934400

#4

Sold to scrap, partially untraceable

Seller: https://backpack.tf/profiles/76561198052906308#!/compare/1529452800/1529625600

Buyer: https://backpack.tf/profiles/76561198135388328#!/compare/1529539200/1529625600

Only 9 keys and 18 ref match. More was involved, but was spent on other items the seller received later that day.

Using unsolds.

On sale for ~12 keys on scrap.tf:

https://i.imgur.com/jYKkBRM.png

https://backpack.tf/item/5300103974

https://backpack.tf/profiles/76561198135388328#!/compare/1529539200/1529625600 - Obtained 22nd June

Going with 12 flat.