Second Suggestion, constructive criticism appreciated.

Scorching Flames Noble Nickel Amassment of Hats:

3 in existence

item 1 history: http://backpack.tf/item/5090978389 (3 usable sales in last 3 months)

item 2 history: https://backpack.tf/item/5008997705 (0 usable sales in last 3 months)

item 3 history: http://backpack.tf/item/2345788067 (0 usable sales in last 3 months)

Only 3 usable sales in last 3 months on item 1:

Sale 1: 20 Nov-15 Dec 2016

Seller: Sold for Phosphorous Dapper = (85 Keys)

http://backpack.tf/profiles/76561198290331062#!/compare/1479600000/1481760000

Dapper: http://backpack.tf/stats/Unusual/Dr's%20Dapper%20Topper/Tradable/Craftable/63

mini:

Sold for a Disco Beat Down Dark Falkirk Helm (80-100 keys, in date)

http://backpack.tf/profiles/76561198162463523#!/compare/1484611200/1484697600

Sale 2: 14-16 dec 2016

Seller: Purple conf helm (13, 16 when sold) + Duped PE Hallmark (91)+ aussie tomislav (13) = (13+91+13=117 keys)

http://backpack.tf/profiles/76561198056468036#!/compare/1481673600/1481760000

The only recent sale I could find on the Hallmark @62 keys sold to a quickbuyer:

More details here:

https://backpack.tf/suggestion/585969fae338773f211aacd8

Buyer (Hard to separate out the trade):

http://backpack.tf/profiles/76561198239021024#!/compare/1481673600/1481846400

{Excluding sale 2}

Sale 3: 19-20 dec 2016

Buyer:Bought for CTF Dapper ( 49.5 keys, in-date) + PE Tam O'Shanter (40.5 keys, in date) = (49.5+40.5=90 keys)

http://backpack.tf/profiles/76561198289814059#!/compare/1482019200/1482192000 (7 keys came from another person)

Seller (Hard to separate out the trade):

http://backpack.tf/profiles/76561198239021024#!/compare/1482105600/1482364800

Classifieds @90 Keys:

http://backpack.tf/classifieds?item=Noble%20Nickel%20Amassment%20of%20Hats&quality=5&tradable=1&craftable=1&australium=-1&particle=14

{Excluding due to the seller being a scammer}

Rounding it off to 85-90 Keys using Sale 1 and Sale 3.

Thanks to Pampick and Foamy for the help.