Sale 1:

Sold for Kill-a-Watt Virtual Reality Headset (17) + 3 keys + Schadenfreude (~1)

No outpost

Seller: https://backpack.tf/profiles/76561198137968592#!/compare/1492128000/1492214400

Buyer: https://backpack.tf/profiles/76561198067055238#!/compare/1492128000/1492214400

X = 21

Sale 2:

Sold for Circling Heart Shooter’s Sola Topi (Mini at 16.5 below) + ~4 keys in items

http://www.tf2outpost.com/trade/28855238 - B/O of 22

Seller: https://backpack.tf/profiles/76561198129220361#!/compare/1490572800/1491004800

Buyer: https://backpack.tf/profiles/76561198087172601#!/compare/1490918400/1491004800

X = 21

Sale 3:

Sold for Purple Confetti Armoured Authority (Mini at 18.5 below) + >0.5 keys in painted items

No outpost

Seller: https://backpack.tf/profiles/76561198112909836#!/compare/1493769600/1493856000

Buyer: https://backpack.tf/profiles/76561197964499284#!/compare/1493683200/1493769600

X = 19

Sale 4:

Bulk

Seller: https://backpack.tf/profiles/76561198208062409#!/compare/1497398400/1497484800

Buyer: https://backpack.tf/profiles/76561198335680035#!/compare/1497398400/1497484800

Sale 5:

Sold for Orbiting Fire Slick Cut + 3 keys

http://www.tf2outpost.com/trade/28856965 - B/O of 23

Seller: https://backpack.tf/profiles/76561198087172601#!/compare/1491004800/1491091200

Buyer: https://backpack.tf/profiles/76561198137968592#!/compare/1490918400/1491091200

Was used on the Slick.

Sale 6:

Sold for Infernal Smoke Most Wanted

Seller: https://backpack.tf/profiles/76561198067055238#!/compare/1492214400/1492300800

Buyer: https://backpack.tf/profiles/76561198009272632#!/compare/1492214400/1492300800

Should be used on the taunt.

Purple Confetti Authority Mini:

https://backpack.tf/suggestion/594d27b2cf6c75431b7ae450

Circling Heart Topi Mini:

https://backpack.tf/suggestion/594d3c25cf6c7571046ddc67

Sellers:

20 keys:

http://i.imgur.com/9EuJr1g.png - 21 days

https://backpack.tf/u/76561198073515220

23 keys:

http://i.imgur.com/rvYvXd2.png - 1 month

https://backpack.tf/u/76561198009272632

24 keys:

http://i.imgur.com/m0DK7DH.png - 4 days, definitely lowered/re-listed

https://backpack.tf/item/4815833248

https://backpack.tf/u/76561197964171516

http://www.tf2outpost.com/trade/29233440

Offers:

http://www.tf2outpost.com/trade/28863814 - 2 months

https://backpack.tf/u/76561197991208302

Sales at:

19

21 (2x)

Going with 19-21.