I have 2 reasons, why in my opinion price of this hat should about 12 keys. Here are my points:

1.So, this tradeing history is kinda complicated, so let me start from beggining. I got this hat 1 for 1 for fat mans field hat terror- wat effect (Screenshot 1)(Unpriced). Fat mans field cap was an outcome of trade 1 for 1 for Terror-Wat Pugilist's Protector (value of about 12 keys)(Screenshot 2)(Value proof:https://backpack.tf/stats/Unusual/Pugilist%27s%20Protector/Tradable/Craftable/57). That's why from this point of view we will take price on about 12 keys.

2.Second estimated value we will take from similar effect hat: green confetti one. Its priced on around 11.5 key, but green confetti one is more common (10 known in existence), when there are only 2 of purple confetti effect. Thats why i would price at at about 12 keys too.

Summarizing the price should be around 12 keys.This hat should be priced, because it makes tradeing in general much easier.

Sorry for bad quality and white bars, but i did it in Paint :)

Screenshot 1A:https://imgur.com/XfkA0uv

Screenshot 1B:https://imgur.com/1VLUF43

Screenshot 2A:https://imgur.com/EgOukFB

Screenshot 2B:https://imgur.com/pN79QrA

Ps. If i forgot anything, or you would like to say what is wrong with this price suggestion, feel free to comment.

Thanks for attention.