Sale 1:

Sold for Peace Sign Handyman's Handle (Mini at 9 below) + 2 keys

http://www.tf2outpost.com/trade/29349357 - B/O of 12

Seller: https://backpack.tf/profiles/76561198409556771#!/compare/1503878400/1503964800

Buyer: https://backpack.tf/profiles/76561198127973248#!/compare/1503878400/1503964800

X = 11

Sale 2:

Quicksold for 9 keys + ~1 key in items

No outpost

Seller: https://backpack.tf/profiles/76561198170990055#!/compare/1503187200/1503273600

Buyer: https://backpack.tf/profiles/76561198148875540#!/compare/1503187200/1503273600

X = 10

Sale 3:

Quicksold for 10 keys (IDs match)

No outpost

Seller: https://backpack.tf/profiles/76561198117354105#!/compare/1503619200/1503878400

Buyer: https://backpack.tf/profiles/76561198126743432#!/compare/1503792000/1503878400

X = 10

Sale 4:

Quicksold for 9 keys + maybe some ref

Seller: https://backpack.tf/profiles/76561198027384016#!/compare/1503187200/1503273600

Buyer: https://backpack.tf/profiles/76561198170990055#!/compare/1503187200/1503273600

X = 9

Sale 5:

Sold with ~5 keys in pure/items for Purple Confetti Stainless Pot

Seller: https://backpack.tf/profiles/76561198197568798#!/compare/1502409600/1503187200

Buyer: https://backpack.tf/profiles/76561198027384016#!/compare/1503100800/1503187200

Shouldn't be used here. Buyers at 9 anyways, which is what this would end up being if used here.

Peace Sign Handle Mini:

Sold for 9 keys + 14 ref

No outpost

Seller: https://backpack.tf/profiles/76561198304138933#!/compare/1505865600/1505952000

Buyer: https://backpack.tf/profiles/76561198097409973#!/compare/1505865600/1505952000

X = 9

Sellers:

11 keys:

https://i.imgur.com/4X0Lpps.png - 1 month

Sales at:

9

10 (2x)

11

9 quicksold, and there are plenty of buyers at 9. Excluding 9.

Would normally exclude 10, but there is only one sale for higher, and the seller at 11 is (at least) a month old. Would also normally exclude 11 with that unsold, but the only sales for lower are quicksales.

Going with 10-11.