Sale 1:

https://backpack.tf/profiles/76561198125791160#!/compare/1590969600/1591056000

https://backpack.tf/profiles/76561198125950723#!/compare/1590969600/1591056000

Sold for 17 keys

sale 2:

https://backpack.tf/profiles/76561198125950723#!/compare/1596153600/1596585600

https://backpack.tf/profiles/76561198116344334#!/compare/1596499200/1596585600

Sold for 21 keys

sale 3:

https://backpack.tf/profiles/76561198864903457#!/compare/1596672000/1596758400

https://backpack.tf/profiles/76561198410123158#!/compare/1596672000/1596758400

https://backpack.tf/profiles/76561197972273299#!/compare/1596672000/1596758400

https://backpack.tf/profiles/76561198269337198#!/compare/1596672000/1596758400

https://backpack.tf/profiles/76561198859832739#!/compare/1596672000/1596758400

Scammer / Scammer ALT / Bulk

sale 4:

https://backpack.tf/profiles/76561198859832739#!/compare/1596758400/1596844800

https://backpack.tf/profiles/76561198122393901#!/compare/1596672000/1596844800

Untrace / Bulk

sale 5:

https://backpack.tf/profiles/76561198212072039#!/compare/1596499200/1596672000

https://backpack.tf/profiles/76561198350879574#!/compare/1596412800/1596499200

https://backpack.tf/profiles/76561198966838493#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561198211647572#!/compare/1596585600/1596672000

Untrace / QS

sale 6:

https://backpack.tf/profiles/76561198211647572#!/compare/1596585600/1596672000

https://backpack.tf/profiles/76561198080179568#!/compare/1596585600/1596672000

Untrace / QS

Sale 7:

https://backpack.tf/profiles/76561198080179568#!/compare/1596585600/1596672000

https://backpack.tf/profiles/76561198126695508#!/compare/1596499200/1596672000

Untrace / Bulk

sale 8:

https://backpack.tf/profiles/76561198126695508#!/compare/1596758400/1596672000

https://backpack.tf/profiles/76561198097171432#!/compare/1596758400/1596672000

https://backpack.tf/profiles/76561198080179568#!/compare/1596758400/1596844800

Untrace / QS

sale 9:

https://backpack.tf/profiles/76561198395511763#!/compare/1589587200/1589673600

https://backpack.tf/profiles/76561199050326472#!/compare/1589587200/1589673600

Sold with 3 keys for DBD Eye

Eye Mini:

https://backpack.tf/suggestion/5f30eaa64f3a86111e380ea4

Suggestion for 19.5 keys

Total is 16.5 keys

sale 10:

https://backpack.tf/profiles/76561199050326472#!/compare/1589587200/1589673600

https://backpack.tf/profiles/76561198360368546#!/compare/1589587200/1589760000

Sold for 18 keys

sale 11:

https://backpack.tf/profiles/76561198360368546#!/compare/1589846400/1590019200

https://backpack.tf/profiles/76561198095862827#!/compare/1589760000/1589846400

QS

sale 12:

https://marketplace.tf/items/tf2/30355;5;u58

$29.99 / $1.99 = 15.07 keys

https://backpack.tf/item/7956100316

Total sales @:

15, 17, 17, 18, 21 keys

buyers up to ~8.5 keys,

given that one of the 18 sales resold within the same day as a QS;

calling 21 high (note that this also took some months to sell),

15 low to balance,

taking 17 - 18 keys.