Sale 1:

https://backpack.tf/profiles/76561198046393528#!/compare/1566518400/1566604800

https://backpack.tf/profiles/76561198112444760#!/compare/1563840000/1566604800

https://backpack.tf/profiles/76561198120579245#!/compare/1566432000/1566604800

https://backpack.tf/profiles/76561198059797730#!/compare/1566518400/1566604800

https://backpack.tf/profiles/76561198273865118#!/compare/1566518400/1566604800

https://backpack.tf/profiles/76561198155441223#!/compare/1566518400/1566691200

https://backpack.tf/profiles/76561198964658472#!/compare/1566259200/1566691200

https://backpack.tf/profiles/76561198155441223#!/compare/1566518400/1566691200

https://backpack.tf/profiles/76561198037674114#!/compare/1566777600/1570147200

Untrace / gambling

Sale 2:

https://backpack.tf/profiles/76561198037674114#!/compare/1567209600/1570147200

https://backpack.tf/profiles/76561198801634335#!/compare/1570579200/1570665600

https://backpack.tf/profiles/76561198044872043#!/compare/1570492800/1570579200

Untrace

sale 3:

https://backpack.tf/profiles/76561198095539073#!/compare/1570579200/1570665600

https://backpack.tf/profiles/76561198872628170#!/compare/1570579200/1570665600

https://backpack.tf/profiles/76561198067025442#!/compare/1570665600/1570752000

https://backpack.tf/profiles/76561198403259580#!/compare/1570665600/1570752000

Gambling

Sale 4:

https://backpack.tf/profiles/76561198089253101#!/compare/1571356800/1571443200

https://backpack.tf/profiles/76561198080179568#!/compare/1571356800/1571443200

QS

sale 5:

https://backpack.tf/profiles/76561197990296209#!/compare/1557014400/1571356800

https://backpack.tf/profiles/76561198075579476#!/compare/1571529600/1573344000

Untrace

sale 6:

https://backpack.tf/profiles/76561198147322105#!/compare/1573257600/1573344000

https://backpack.tf/profiles/76561198416724843#!/compare/1572998400/1573257600

Utnrace

Sale 7:

https://backpack.tf/profiles/76561198416724843#!/compare/1572998400/1573257600

https://backpack.tf/profiles/76561198253483866#!/compare/1573171200/1573257600

Sold in bulk for keys

Sale 8:

https://backpack.tf/profiles/76561198253483866#!/compare/1573171200/1573257600

https://backpack.tf/profiles/76561198334946156#!/compare/1573171200/1573257600

Bulk

sale 9:

https://backpack.tf/profiles/76561198334946156#!/compare/1573257600/1573344000

https://backpack.tf/profiles/76561198123912038#!/compare/1573257600/1573344000

Sold for 8 keys

Sale 9:

https://backpack.tf/profiles/76561198123912038#!/compare/1573344000/1573430400

https://backpack.tf/profiles/76561198249078668#!/compare/1573344000/1573430400

Sold for 9 keys

Sale 10:

https://backpack.tf/profiles/76561198249078668#!/compare/1573344000/1573430400

https://backpack.tf/profiles/76561198363395191#!/compare/1573344000/1573430400

QS for 7 keys

Sale 11:

https://backpack.tf/profiles/76561198363395191#!/compare/1573430400/1573516800

https://backpack.tf/profiles/76561198051798340#!/compare/1573430400/1573516800

Untrace

Sale 12:

https://backpack.tf/profiles/76561198309832044#!/compare/1571097600/1571184000

https://backpack.tf/profiles/76561198330901094#!/compare/1571875200/1572480000

SCM

Sale 13:

https://backpack.tf/profiles/76561198330901094#!/compare/1572566400/1572652800

https://backpack.tf/profiles/76561198360770134#!/compare/1569974400/1572652800

Bulk

sale 14:

https://backpack.tf/profiles/76561198318781669#!/compare/1568160000/1569283200

https://backpack.tf/profiles/76561198140559050#!/compare/1568419200/1568505600

Untrace

Sale 15:

https://backpack.tf/profiles/76561198140559050#!/compare/1568505600/1568592000

https://backpack.tf/profiles/76561198211068823#!/compare/1568419200/1568505600

Either C9 Letch or Miami Bot Dogger...

Sale 16:

https://backpack.tf/profiles/76561198211068823#!/compare/1569715200/1569801600

https://backpack.tf/profiles/76561198106511423#!/compare/1569715200/1569888000

Sold with ~2 keys in sweets for Bubbling Cannonball(15)

Total is 13 keys

Sale 17:

https://backpack.tf/profiles/76561198106511423#!/compare/1572825600/1572912000

https://backpack.tf/profiles/76561198114649692#!/compare/1572825600/1572912000

Sold for 10 keys

Sale 18:

https://backpack.tf/profiles/76561198114649692#!/compare/1572912000/1573084800

https://backpack.tf/profiles/76561198289040457#!/compare/1572998400/1573084800

Untrace... Toque doesn't history match...

Sale 19:

https://backpack.tf/profiles/76561198289040457#!/compare/1572998400/1573084800

https://backpack.tf/profiles/76561198240537922#!/compare/1572998400/1573084800

Keys

sale 20:

https://backpack.tf/profiles/76561198240537922#!/compare/1572998400/1573084800

https://backpack.tf/profiles/76561198129380689#!/compare/1572998400/1573084800

https://backpack.tf/profiles/76561198089253101#!/compare/1572998400/1573084800

Utnrace

sale 21:

https://backpack.tf/profiles/76561198081042493#!/compare/1567036800/1567123200

https://backpack.tf/profiles/76561198252999692#!/compare/1567036800/1567123200

Sold for 8 keys

Sale 22:

https://backpack.tf/profiles/76561198252999692#!/compare/1567382400/1567468800

https://backpack.tf/profiles/76561198380596866#!/compare/1567468800/1570233600

Sold for DBD HWAH + ~1 key in sweets

use there

Sale 23:

https://backpack.tf/profiles/76561198380596866#!/compare/1572048000/1572220800

https://backpack.tf/profiles/76561197964171516#!/compare/1572134400/1572220800

Sold with ~1 key in sweets for KaW Rouser

use there

Sale 24, 25:

https://marketplace.tf/items/tf2/251;5;u56

$19.99 / $1.83 = 10.92 keys <--- https://backpack.tf/item/4164388284 | https://bot.tf/stats/listings/4OV683WJ B/O of 16 keys

$16 / $1.80 = 8.89 keys

Total sales @:

8, 8, 8.89, 9, 10, 10.92, 13 keys

buyers up to ~7.5 keys,

near month unsold for 12 keys,

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

new seller for 10 keys,

let's go with 8 - 11 keys.