Sale 1:

https://backpack.tf/profiles/76561198332403634#!/compare/1546041600/1546214400

https://backpack.tf/profiles/76561198363395191#!/compare/1546041600/1546214400

QS

Sale 2:

https://backpack.tf/profiles/76561198115372881#!/compare/1548288000/1549152000

https://backpack.tf/profiles/76561198092378391#!/compare/1547078400/1549497600

Untrace

Sale 3:

https://backpack.tf/profiles/76561198833954279#!/compare/1545264000/1545350400

https://backpack.tf/profiles/76561198311725787#!/compare/1545264000/1545350400

Can only trace 3 ref

Sale 4:

https://backpack.tf/profiles/76561198129117639#!/compare/1547164800/1549152000

https://backpack.tf/profiles/76561198335426817#!/compare/1549238400/1549324800

SCM

Sale 5:

https://backpack.tf/profiles/76561198335791307#!/compare/1547164800/1547251200

https://backpack.tf/profiles/76561198310007387#!/compare/1546128000/1547769600

Sold for FoD Wanted + 11 ref

Use there, enough proof for that.

Sale 6:

https://backpack.tf/profiles/76561198084871957#!/compare/1548806400/1549152000

made unusual

Sale 7:

https://backpack.tf/profiles/76561198082869799#!/compare/1545696000/1545782400

https://backpack.tf/profiles/76561198362983846#!/compare/1545782400/1545868800

Untrace

Sale 8:

https://backpack.tf/profiles/76561198363395191#!/compare/1545436800/1545523200

https://backpack.tf/profiles/76561198448443559#!/compare/1545436800/1545955200

SCM

Sale 9:

https://backpack.tf/profiles/76561198448443559#!/compare/1545955200/1546387200

https://backpack.tf/profiles/76561198124222069#!/compare/1546041600/1546560000

SCM

Sale 10:

https://backpack.tf/profiles/76561198315110829#!/compare/1548460800/1548892800

https://backpack.tf/profiles/76561198039605762#!/compare/1548201600/1549152000

SCM

Sale 11:

https://backpack.tf/profiles/76561198832761255#!/compare/1542499200/1542585600

https://backpack.tf/profiles/76561198112820972#!/compare/1542240000/1542758400

Bulked

Sale 12:

https://backpack.tf/profiles/76561198112820972#!/compare/1543190400/1544140800

https://backpack.tf/profiles/76561198002757046#!/compare/1543708800/1543795200

Sold for 3 keys + 33 ref

Total is 3.75 keys

Sale 13:

https://backpack.tf/profiles/76561198002757046#!/compare/1544313600/1544400000

'https://backpack.tf/profiles/76561198044335614#!/compare/1544313600/1544400000

Untrace

Sale 14:

https://backpack.tf/profiles/76561198044335614#!/compare/1546214400/1546300800

https://backpack.tf/profiles/76561198044335614#!/compare/1546214400/1546300800

SCM

Sale 15:

https://backpack.tf/profiles/76561198280837376#!/compare/1549411200/1549756800

https://backpack.tf/profiles/76561198208047597#!/compare/1549670400/1549756800

Bulk

Sale 16:

https://backpack.tf/profiles/76561198208047597#!/compare/1549670400/1549756800

https://backpack.tf/profiles/76561198208047597#!/compare/1549670400/1549756800

https://backpack.tf/profiles/76561198120768380#!/compare/1549670400/1549756800

https://backpack.tf/profiles/76561198147414741#!/compare/1549584000/1549756800

Bulked.

Sale 17:

https://backpack.tf/profiles/76561198147414741#!/compare/1549756800/1549843200

https://backpack.tf/profiles/76561198161562033#!/compare/1549756800/1549843200

Sold with ~2 keys in sweets for 6 keys

Total is 4 keys, void by Sale 18.

Sale 18:

https://backpack.tf/profiles/76561198161562033#!/compare/1549843200/1550102400

https://backpack.tf/profiles/76561198305676157#!/compare/1549843200/1549929600

QS

Sale 19:

https://backpack.tf/profiles/76561198252911139#!/compare/1543708800/1543795200

https://backpack.tf/profiles/76561198177872379#!/compare/1543708800/1543795200

Sold for Spell + 23 ref

Sale 20:

https://backpack.tf/profiles/76561198177872379#!/compare/1543795200/1543881600

https://backpack.tf/profiles/76561198121184573#!/compare/1543017600/1543881600

Sold for 4 keys

Sale 21:

https://backpack.tf/profiles/76561198026129220#!/compare/1543190400/1543276800

https://backpack.tf/profiles/76561198115721685#!/compare/1543190400/1543363200

Untrace

Sale 22:

https://backpack.tf/profiles/76561198026129220#!/compare/1544313600/1544400000'

https://backpack.tf/profiles/76561198044347430#!/compare/1542758400/1546646400

Untrace

Sale 23:

https://backpack.tf/profiles/76561198198564130#!/compare/1543622400/1543708800

https://backpack.tf/profiles/76561198057582763#!/compare/1543622400/1543708800

https://backpack.tf/profiles/76561198115721685#!/compare/1543536000/1543622400

Untrace

Sale 24:

https://backpack.tf/profiles/76561198305676157#!/compare/1542758400/1542844800

https://backpack.tf/profiles/76561198026129220#!/compare/1542672000/1542758400

Untrace

Sale 25:

https://backpack.tf/profiles/76561198024152496#!/compare/1543276800/1543363200

https://backpack.tf/profiles/76561198115721685#!/compare/1543190400/1543363200

Untrace

Sale 26:

https://backpack.tf/profiles/76561198271936634#!/compare/1542844800/1543190400

https://backpack.tf/profiles/76561198804284101#!/compare/1544572800/1546300800

Untrace, missing an inbetween, then SCM

Sale 27:

https://backpack.tf/profiles/76561198154332450#!/compare/1542758400/1548633600

https://backpack.tf/profiles/76561198115372881#!/compare/1544832000/1548288000

SCM

Sale 28:

https://backpack.tf/profiles/76561198259052169#!/compare/1544572800/1549411200

https://backpack.tf/profiles/76561198129117639#!/compare/1543363200/1546387200

Untrace

Sale 29 - 42:

https://marketplace.tf/items/30614;5;u3004

$7.99 / $1.73 = 4.62 keys (x2)

$7.99 / $1.72 = 4.65 keys

$5.45 / $1.72 = 3.17 keys

$7.99 / $1.73 = 4.62 keys

$5.45 / $1.73 = 3.15 keys

$7.49 / $1.71 = 4.38 keys (x3)

$19.99 / $1.71 = 11.69 keys

$5.45 / $1.72 = 3.17 keys

$7.49 / $1.72 = 4.35 keys

$7.00 / $1.72 = 4.07 keys

$5.45 / $1.68 = 3.24 keys (x2)

$5.46 / $1.65 = 3.31 keys

$7.49 / $1.65 = 4.54 keys

$6.9 / $1.8 = 3.83 keys

$6.89 / $1.8 = 3.83 keys

$6.99 / $1.79 = 3.91 keys

$8 / $1.77 = 4.52 keys

$6 / $1.75 = 3.43 keys

Total sales @:

3.15 keys

3.17 (x2) keys

3.24 (x2) keys

3.31 keys

3.43 keys

3.75 keys

3.83 keys

3.91 keys

4 keys

4.08 keys

4.35 keys

4.38 (x3) keys

4.52 keys

4.54 keys

4.62 (x3) keys

4.65 keys

11.69 keys

Buyers up to 3.48 keys,

newish seller for 3.57, older one for ~5 keys,

rounding 3.75 up,

rounding 4.65 down,

going with 4 - 4.5 keys