Sale 1:

Sold for Green Energy Larrikin Robin (37) + Aussie SMG (7) + 3 keys + ~2 keys in metal + ~2 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561198189121381#!/compare/1500854400/1500940800

Buyer: https://backpack.tf/profiles/76561198101160938#!/compare/1500854400/1500940800

X = 51

Sale 2:

Sold with ~1 key in items for Green Black Hole Big Chief (65)

http://www.tf2outpost.com/trade/29277813 - B/O of 48

Seller: https://backpack.tf/profiles/76561198087175689#!/compare/1500076800/1500163200

Buyer: https://backpack.tf/profiles/76561198189121381#!/compare/1500076800/1500163200

X = 48 (Capped by B/O)

Sale 3:

Sold for 25 keys + Catastrophic Companions (<21) + ~1.5 keys in taunts

No outpost

Seller: https://backpack.tf/profiles/76561198166102098#!/compare/1502582400/1502668800

Buyer: https://backpack.tf/profiles/76561198038467413#!/compare/1502582400/1502668800

X = 47

Sale 4:

Sold for Searing Plasma Your Worst Nightmare (40.5) + <6 keys in items

No outpost

Seller: https://backpack.tf/profiles/76561197981169870#!/compare/1499385600/1499472000

Buyer: https://backpack.tf/profiles/76561198061489334#!/compare/1499299200/1499385600

X = 47

Sale 5:

Sold for Purple Energy Vintage Merryweather (Suggestion at 38.5) + 4 keys

No outpost

Seller: https://backpack.tf/profiles/76561198075197384#!/compare/1500076800/1500163200

Buyer: https://backpack.tf/profiles/76561198087175689#!/compare/1500076800/1500163200

X = 43

Sale 6:

Sold with 1 key + vintage flare gun (<0.5) for Terror-Watt Hermes (21) + Purple Confetti Tossle Cap (Suggestion at 21, should be 23)

http://www.tf2outpost.com/trade/29243709 - B/O of 45

Seller: https://backpack.tf/profiles/76561198083363051#!/compare/1498435200/1498521600

Buyer: https://backpack.tf/profiles/76561198037947164#!/compare/1498348800/1498521600

X = 43

Sale 7:

Sold for 39 keys (Buyer's compare link)

No outpost

Seller: https://backpack.tf/profiles/76561198344491537#!/compare/1498262400/1498348800

Buyer: https://backpack.tf/profiles/76561197964171516#!/compare/1498262400/1498348800

X = 39

Sale 8:

Sold for 38 keys

http://www.tf2outpost.com/trade/29200105 - Deleted B/O, nothing cached

Seller: https://backpack.tf/profiles/76561198048008254#!/compare/1496275200/1496361600

Buyer: https://backpack.tf/profiles/76561198065224856#!/compare/1496275200/1496361600

X = 38

Sale 9:

Quicksold for 36 keys

Seller: https://backpack.tf/profiles/76561198089437725#!/compare/1498176000/1498262400

Buyer: https://backpack.tf/profiles/76561198083363051#!/compare/1498176000/1498262400

X = 36

Sale 10:

Bulk for Tesla Coil Merc's Mohawk

Seller: https://backpack.tf/profiles/76561198065224856#!/compare/1498089600/1498176000

Buyer: https://backpack.tf/profiles/76561198089437725#!/compare/1498089600/1498176000

Sale 11:

Bulk for things

Seller: https://backpack.tf/profiles/76561198061489334#!/compare/1499990400/1500076800

Buyer: https://backpack.tf/profiles/76561198075197384#!/compare/1499990400/1500076800

Purple Energy Merryweather:

https://backpack.tf/suggestion/599c17aecf6c7556ef510b0f

Purple Confetti Tossle:

https://backpack.tf/suggestion/59964f71cf6c75180d6bc4dd - refer to my comment

Sellers:

48 keys:

http://i.imgur.com/vLN10ni.png - 3 months

Sales at:

36

38

39

43 (2x)

47 (2x)

48

51

36 quicksold. Excluding 36.

3 month old seller at 48. Excluding 48 and 51.

Going with 38-47.