Sale 1:

https://backpack.tf/profiles/76561198258559685#!/compare/1568851200/1583798400

https://backpack.tf/profiles/76561198995920102#!/compare/1586822400/1586908800

Untrace

sale 2:

https://backpack.tf/profiles/76561198820994977#!/compare/1588636800/1588723200

https://backpack.tf/profiles/76561198061652621#!/compare/1529971200/1591315200

untrace

sale 3:

https://backpack.tf/profiles/76561198191779491#!/compare/1589155200/1589241600

https://backpack.tf/profiles/76561198138697433#!/compare/1586995200/1589328000

SCM

sale 4:

https://backpack.tf/profiles/76561198989947414#!/compare/1581379200/1584576000

https://backpack.tf/profiles/76561198011321852#!/compare/1584489600/1584576000

Bulk

sale 5:

https://backpack.tf/profiles/76561198011321852#!/compare/1587254400/1587340800

https://backpack.tf/profiles/76561198280059345#!/compare/1586995200/1587340800

Sold for ~12 keys

sale 6 - 11:

https://marketplace.tf/items/tf2/1118;5;u3009

$14.33 / $1.69 = 8.48 keys <--- https://backpack.tf/item/3886493461 | https://bot.tf/stats/listings/Y3WWL6R0 B/O of ~11.5 keys

$19.6 / $1.69 = 11.60 keys <--- https://backpack.tf/item/2766487566

$18.22 / $1.75 = 10.41 keys

$18.22 / $1.77 = 10.29 keys <--- https://backpack.tf/item/7453334488

$18.04 / $1.77 = 10.19 keys

$14.42 / $1.82 = 7.92 keys

Sale 12:

https://backpack.tf/profiles/76561198204215085#!/compare/1587168000/1588377600

https://backpack.tf/profiles/76561198358296372#!/compare/1588291200/1588377600

QS

sale 13:

https://backpack.tf/profiles/76561198358296372#!/compare/1588464000/1588550400

https://backpack.tf/profiles/76561198441327899#!/compare/1581379200/1589932800

Sold for 11 keys

sale 14:

https://backpack.tf/profiles/76561198441327899#!/compare/1589932800/1590537600

https://backpack.tf/profiles/76561198358296372#!/compare/1589932800/1590019200

QS soon after Sale 13

sale 14:

https://backpack.tf/profiles/76561198340634356#!/compare/1583884800/1583971200

https://backpack.tf/profiles/76561198077870175#!/compare/1583884800/1583971200

Sold for 16 keys

sale 15:

https://backpack.tf/profiles/76561198334598690#!/compare/1586649600/1586736000

https://backpack.tf/profiles/76561198076218381#!/compare/1586649600/1586995200

Sold for 11 keys

Total sales @:

8, 8.5, 10, 10, 10, 11, 11, 12, 12, 16 keys

buyers up to ~9.5 keys,

one high buyer at 11 keys,

universal buyers null, as higher than most buyers for non-universal.

Let's try 10 - 12 keys.