Hey, this suggestion is an improvement of the recent suggestion that lacked evidence and much fact.

This unusual has also been scanned in another backpack, making it a 1 of 2 in the world unusual. But at the moment I think it is fair to count it as the 1 of 1 in the market unusual. The pipe's history is shown here if there are still other trades showing the exact unusual.

History: http://backpack.tf/item/3224682343

Now here comes the evidence for what this unusual sold for.

http://cloud-4.steampowered.com/ugc/544139766546665469/C8C3403B3A4C8B74C4BE6490AD772B659D48B0A1/

The person who traded the pipe for it, possibly currently has is a Orbiting Fire Ol' Geezer and a bill's hat from this unusual. The Ol' Geezer is priced at 11-12 keys, and the Bill's hat is priced at 3 keys(Not sure what to do about the paint).

Unusual History: http://backpack.tf/item/1841473468

Pink-Bill's Hat History: http://backpack.tf/item/43641663

Respecting the price of the geezer which is 11-12 + a 3 key Bill's hat, this unusual could be fairly priced at 14-15 keys.

Also considering how it is related, but less than the Phosphorous-effect price wise.

If I am missing any important factors, or if you have critical responses please post below in the comments.