This one took me quite the while.

-1:1'd for a neutron toque, using to price the toque: http://backpack.tf/profiles/76561198025486280#!/compare/1478217600/1478390400

-sold for 16 pure: http://backpack.tf/profiles/76561198000536564#!/compare/1478390400/1478476800

-sold for 30 keys?: http://backpack.tf/profiles/76561197963500354#!/compare/1480982400/1481068800

-sold for 15 keys: http://backpack.tf/profiles/76561198115325995#!/compare/1480982400/1481068800

-sold w/ one key for an atomic head full(21 keys) (20 total): http://backpack.tf/profiles/76561198060136479#!/compare/1476403200/1476489600

-sale above capped at 19 thanks to a B/O: http://www.tf2outpost.com/trade/28500840

-???: http://backpack.tf/profiles/76561198120603585#!/compare/1476489600/1476576000

-1:1'd for a stormy dixie: http://backpack.tf/profiles/76561198220101208#!/compare/1478476800/1478563200 (this is likely an outlier, as there is one for sale on OP for under 15 keys for over 2 weeks now: http://www.tf2outpost.com/trade/28619520 )

-???, didn't involve the scrap: http://backpack.tf/profiles/76561198126480635#!/compare/1478476800/1478563200

-???: http://backpack.tf/profiles/76561198078594336#!/compare/1478822400/1478908800

Taking 16-19 thanks to the sales above. It would normally be 15-19, but there's a buyer on the classies at 15, indicating that 15 is low: https://i.gyazo.com/211e5b8e6658060cdd1ee7ba2773637c.gif (profile: http://backpack.tf/u/76561198056753441 )