High energy hat.

Sold for a Neutron Star Wing Mann(10 Keys)

http://backpack.tf/profiles/76561198044022698#!/compare/1489276800/1489363200

Sold for 11.5 Keys

http://backpack.tf/profiles/76561198017897278#!/compare/1489968000/1490227200

Sold for 11 Keys

http://backpack.tf/profiles/76561198073472840#!/compare/1489622400/1489708800

Sold for 11 Keys

http://backpack.tf/profiles/76561198161377371#!/compare/1489968000/1490140800

Sold for 10 Keys

http://backpack.tf/profiles/76561198304138933#!/compare/1490400000/1490486400

Sold for 11 Keys

http://backpack.tf/profiles/76561198137326099#!/compare/1486252800/1486339200

http://backpack.tf/item/5272388421

Sold for 12.5 Keys

http://backpack.tf/profiles/76561198006608659#!/compare/1487203200/1487289600

Sold for 13 Keys(1 Key was in metal)

http://backpack.tf/profiles/76561198344933095#!/compare/1486857600/1486944000

Sold for 11 Keys

http://backpack.tf/profiles/76561198132046444#!/compare/1486857600/1486944000

Sold for 12 Keys

http://backpack.tf/profiles/76561198037360212#!/compare/1488672000/1488844800

Sold for 11 Keys

http://backpack.tf/profiles/76561198093617997#!/compare/1487894400/1488240000

Sold for 8 Keys and ~3 Keys in Sweets(11 Keys total)

http://backpack.tf/profiles/76561198075970209#!/compare/1489881600/1490140800

Sold for 11 Keys

http://backpack.tf/profiles/76561198114959212#!/compare/1490227200/1490313600

Sold for 13 Keys

http://backpack.tf/profiles/76561198149087587#!/compare/1490745600/1490832000

Sold for 10 Keys

http://backpack.tf/profiles/76561198328180739#!/compare/1490832000/1490918400

Sold for 10 Keys

http://backpack.tf/profiles/76561198373042400#!/compare/1491004800/1491091200

Sold for 9 Keys

http://backpack.tf/profiles/76561198170710713#!/compare/1487635200/1487721600

Sold for 12 Keys

http://backpack.tf/profiles/76561198075970209#!/compare/1488585600/1488672000

Sold for 11 Keys

http://backpack.tf/profiles/76561198304138933#!/compare/1489104000/1489190400

Sold for 10 Keys

http://backpack.tf/profiles/76561198234377776#!/compare/1491609600/1491696000

Sold for 11 Keys

http://backpack.tf/profiles/76561198304138933#!/compare/1491004800/1491091200

Sold for 11 Keys

http://backpack.tf/profiles/76561198312480435#!/compare/1490486400/1490572800

Sold for 11 Keys

http://backpack.tf/profiles/76561198272153621#!/compare/1491955200/1492041600

Sold for 10 Keys

http://backpack.tf/profiles/76561198054422117#!/compare/1491177600/1491264000

Sold for 11 Keys

http://backpack.tf/profiles/76561198062775462#!/compare/1491177600/1491264000

Sold for ~11 Keys in mixed items

http://backpack.tf/profiles/76561198083073025#!/compare/1492214400/1492300800

Sold for 12 Keys and ~1 Key in Sweets(13 Keys total)

http://backpack.tf/profiles/76561198090442608#!/compare/1486598400/1486684800

Sold for 13 Keys

http://backpack.tf/profiles/76561198067055768#!/compare/1486512000/1486598400

Sold for 12 Keys

http://backpack.tf/profiles/76561197963500354#!/compare/1489968000/1490054400

10-13.

Credits to Mindacos for finding the proof. All I did was make the actual suggestion.