Sale 1: Untrace. (SCM)

https://backpack.tf/profiles/76561198202796551#!/compare/1556409600/1556496000

https://backpack.tf/profiles/76561198013222391#!/compare/1555977600/1556496000

Sale 2: ~8 Keys.

Sold For Strange Professional Killstreak Huntsman (7.43k) + Strange Medi Gun (7.22r) + Strange Festivized Specialized Killstreak Aqua Marine Rocket Launcher (Battle Scarred) (12.66r) = 8 Keys.

https://backpack.tf/profiles/76561198174396715#!/compare/1559692800/1561939200

https://backpack.tf/profiles/76561198198678922#!/compare/1559692800/1559779200

Sale 3: ~8 Keys Pure.

https://backpack.tf/profiles/76561198177146103#!/compare/1556323200/1556409600

https://backpack.tf/profiles/76561198317606171#!/compare/1556323200/1556409600

Sale 4: Untrace.

https://backpack.tf/profiles/76561198317606171#!/compare/1559001600/1559088000

https://backpack.tf/profiles/76561198086586483#!/compare/1559088000/1560384000

Sale 5: Untrace.

https://backpack.tf/profiles/76561198088578255#!/compare/1562284800/1562630400

https://backpack.tf/profiles/76561198139411993#!/compare/1563408000/1563494400

Sale 6: Untrace.

https://backpack.tf/profiles/76561198347828925#!/compare/1555891200/1555977600

https://backpack.tf/profiles/76561198341171690#!/compare/1555977600/1556064000

Sale 7: ~8 Keys Pure.

https://backpack.tf/profiles/76561198341171690#!/compare/1558915200/1559001600

https://backpack.tf/profiles/76561198073549508#!/compare/1558915200/1559001600 - Only 8 Keys Matched.

Sale 8: Untarce.

https://backpack.tf/profiles/76561198023598501#!/compare/1559865600/1563321600

https://backpack.tf/profiles/76561198068353701#!/compare/1545868800/1559865600

Sale 9 & 10: Untrace.

https://backpack.tf/profiles/76561198068353701#!/compare/1559865600/1559952000

https://backpack.tf/profiles/76561198055188457#!/compare/1559865600/1559952000

https://backpack.tf/profiles/76561198055188457#!/compare/1559952000/1560038400

https://backpack.tf/profiles/76561198068353701#!/compare/1559952000/1560038400

Sale 11: ~10 Keys Pure.

https://backpack.tf/profiles/76561198055188457#!/compare/1560297600/1560384000

https://backpack.tf/profiles/76561198185397038#!/compare/1560384000/1560470400

Sale 12: Untrace.

https://backpack.tf/profiles/76561198185397038#!/compare/1560816000/1560902400

https://backpack.tf/profiles/76561198333986358#!/compare/1560816000/1560902400

Sale 13: Untrace.

https://backpack.tf/profiles/76561198333986358#!/compare/1560816000/1560902400

https://backpack.tf/profiles/76561198155809272#!/compare/1560556800/1561593600

Sale 14: ~8 Keys Pure.

https://backpack.tf/profiles/76561198341171690#!/compare/1558656000/1558742400

https://backpack.tf/profiles/76561198049007748#!/compare/1556928000/1558742400

Sale 15: Untrace.

https://backpack.tf/profiles/76561198049007748#!/compare/1558742400/1559001600

https://backpack.tf/profiles/76561198121830870#!/compare/1558656000/1558742400

Sale 16: Untrace.

https://backpack.tf/profiles/76561198121830870#!/compare/1558742400/1558828800

https://backpack.tf/profiles/76561198335791307#!/compare/1558742400/1558828800

Markeplace.tf Sales: https://marketplace.tf/items/tf2/31002;5;u120

Sale 17: ~10 Keys.

May 2

$18.00 / $1.82 = 9.89 keys

Sale 18: ~12 Keys.

May 19

$22.22 / $1.81 = 12.28 keys

Sale 19: ~11 Keys.

Jun 24

$21.00 / $1.84 = 11.41 keys

Sale 20: ~12 Keys.

Jun 2

$21.00 / $1.82 = 11.54 keys

Sale 21: ~7.5 Keys.

Jun 8

$13.65 / $1.83 = 7.46 keys

Sale 22: ~11 Keys.

Jul 19

$20.99 / $1.83 = 11.47 keys

Sales: 7.5/8/8/8/8/10/10/11/11/12/12

10.5 Keys Seller is a bit old - https://bot.tf/stats/listings/4JXN1J9M - https://gyazo.com/f3ade0577e62e86e641e2d74e7d423b8

Including 8 as a common trading point.

Going with 8-11 Keys.

Thanks to scourge for the premium!