Take 2

Sale 1: 63 keys pure (thanks for fixing it Marty)

https://backpack.tf/profiles/76561198076020691#!/compare/1494201600/1494288000

https://backpack.tf/profiles/76561198180225575#!/compare/1494288000/1497398400

Sale 2: Sold for Spectral Swirl Taunt: Rock, Paper, Scissors (45)

https://backpack.tf/profiles/76561198088583151#!/compare/1492992000/1493078400

Sale 3: Bulk

https://backpack.tf/profiles/76561198055721127#!/compare/1495584000/1495670400

Sale 4: Sold for Smoking Merc's Mohawk + ~0.5 keys in items --> 59 keys (was also used on the Mohawk but Marty advises to use it regardless)

https://backpack.tf/profiles/76561198082245500#!/compare/1497225600/1497312000

Was used to price Mohawk

Sale 5: Bulk

https://backpack.tf/profiles/76561198182281603#!/compare/1497312000/1497484800

Sale 6: PE Slug + KaW Splitter --> ~65 (credits Marty Birdman)

https://backpack.tf/profiles/76561198088583151#!/compare/1492819200/1492905600

Young seller at 57, matured seller at 60; buyer at 35

http://i.imgur.com/qYLsv7u.png

Sales at 45, 59, 63, 65. 45 and 65 are almost outdated

Suggesting 59-63 (advised by Marty Birdman)