Sale 1:

Sold for 60 keys

http://www.tf2outpost.com/trade/28073727 - No visible B/O

Seller: http://backpack.tf/profiles/76561198090956917#!/compare/1462752000/1462838400

Buyer: http://backpack.tf/profiles/76561198246221128#!/compare/1462838400/1463356800

X = 60

Sale 2:

Sold for 58 keys?

No outpost

Seller: http://backpack.tf/profiles/76561198074924284#!/compare/1463270400/1463356800

Buyer: http://backpack.tf/profiles/76561198123092643#!/compare/1463356800/1463875200

X = 58

Sale 3:

Sold for Death at Dusk Otolaryngologist Mirror (40) + Planets Triboniophorus Tyrannus

http://www.tf2outpost.com/trade/28130075 - B/O of 57

Seller: http://backpack.tf/profiles/76561198074951180#!/compare/1462147200/1462838400

Buyer: http://backpack.tf/profiles/76561197972215762#!/compare/1462665600/1462752000

Tyrannus is outdated, but this sale should still cap at the B/O, most likely

X = 57 (Capped by B/O)

Sale 4:

Sold for 55 keys

http://www.tf2outpost.com/trade/28158621 - B/O of 55

Seller: http://backpack.tf/profiles/76561197987017396#!/compare/1463011200/1463097600

Buyer: http://backpack.tf/profiles/76561198014276989#!/compare/1462060800/1463097600

X = 55

Sellers:

60 keys:

http://puu.sh/pSgOp/f745735268.png - 15 days

http://puu.sh/pSgVb/a9885c47a4.png (Screenshot, in-case the B/O gets deleted)

Sales at:

55

57

58

60

Going with 55-60