This is my first suggestion, sold the hat myself. If there's anything wrong or odd, please tell me! :)

https://backpack.tf/item/3381702131

Sale 1: 32 Keys in Mixed

https://backpack.tf/profiles/76561198097135729#!/compare/1546300800/1549065600

https://backpack.tf/profiles/76561198139831684#!/compare/1548979200/1549065600

Sold for a Dead Presidents Old Man Frost (18 Keys) + 10 Keys Pure + ~5 Keys in Items

Mini for the Old Man Frost: https://backpack.tf/profiles/76561198066311459#!/compare/1548892800/1549670400

Sold to a Collector for 18 Keys Pure, this is the only recent sale in about 7 months.

Sale 2: N/A

https://backpack.tf/profiles/76561198066813088#!/compare/1548633600/1548892800

https://backpack.tf/profiles/76561198024867201#!/compare/1548720000/1548806400

Untraceable

Sale 3: A Disco Beat Down Caribou Companion

https://backpack.tf/profiles/76561198241082898#!/compare/1543708800/1544140800

1:1 for a DBD Caribou (48 Keys)

Mini for the Caribou:

https://backpack.tf/item/7078723268

https://backpack.tf/profiles/76561198074924284#!/compare/1543968000/1544140800

Sold for ~48 Keys Pure

Conclusion:

Untraceable, 32 and 48 Keys

Final Price: 32-48 Keys

I chose this range because the 2 sales are the borders of it and because when I was selling it, I had a buy out of around 38 pure and about 40 in Items. The reason the offer I got was 32 Keys was because of the Dead Presidents Old Man Frost. Although I sold it for 18 Keys Pure, it was technically worth 25 so it would make the offer ~40 Keys in Mixed.