Sale #1:

Sold for a Nuts Snaggle (10.5) + ~0.3 keys in items

http://backpack.tf/profiles/76561198066886790?time=1429686000 (April 22nd)

http://backpack.tf/profiles/76561198066886790?time=1429945200 (April 25th)

Snaggle: http://www.tf2outpost.com/trade/25796057

(10.5 + 0.3) * 0.9 = 9.72; rounded to 10 keys

Sale #2:

http://www.tf2outpost.com/trade/26067092

Sold for 12 keys

Buyer:

http://backpack.tf/profiles/76561198174802815?time=1432710000 (May 27th)

http://backpack.tf/profiles/76561198174802815?time=1432882800 (May 29th)

Seller:

http://backpack.tf/profiles/76561198065369941?time=1432796400 (May 28th)

http://backpack.tf/profiles/76561198065369941?time=1432882800 (May 29th)

Sold in like 2-3 days.

Sale #3:

http://www.tf2outpost.com/trade/25417304

Sold for 10 keys

http://backpack.tf/profiles/76561198160486733?time=1426662000 (March 18th)

http://backpack.tf/profiles/76561198160486733?time=1426748400 (March 19th)

Older sale, but supports lower-end.

Sale #4:

Sold with 4 keys for a Logo Tricorne (outdated)

http://backpack.tf/profiles/76561198066481704?time=1432105200 (May 20th)

http://backpack.tf/profiles/76561198066481704?time=1432191600 (May 21st)

http://www.tf2outpost.com/trade/25980771 Likely offered on the Tricorne here

Could be used to update the Tricorne

Sale #5:

Sold with an O. Fire Lord Cockswain's Pith Helmet (outdated) for a Stormy Defiant Spartan (19.5)

http://backpack.tf/profiles/76561198071629521?time=1430895600 (May 6th)

http://backpack.tf/profiles/76561198071629521?time=1430982000 (May 7th)

Should be an outlier.

Offers:

http://www.tf2outpost.com/trade/25947153 offered 10 keys

http://backpack.tf/item/2925296841 Looks like it has been used in betting a lot, hard to track anything from here.