Sale #1:

http://backpack.tf/profiles/76561198183617811#!/compare/1468627200/1468713600

Sold 1:1 with Ancient Codex Phononaut.

X = 50 keys.

Sale #2:

http://backpack.tf/profiles/76561198183617811#!/compare/1468713600/1469318400

Sold 1:1 with Cauldron Bubbles Ye Olde Baker Boy.

X = 48 keys.

Sale #3:

http://backpack.tf/profiles/76561198149345069#!/compare/1469923200/1470528000

Sold 1:1 with Circling TF Logo Wraith Wrap.

Will use this to update the Wrap.

Sale #4:

http://backpack.tf/profiles/76561198134105703#!/compare/1466726400/1466812800

Sold with 16 pure keys for Purple Energy El Jefe.

Will use to update Jefe.

Summary: 48-50 keys.

Edit: Sorry SpotlightR, didnt see your plans about this hat in the Baker Boy's suggestion.