Thanks to F⌬amy the Fearsome for the extra info.

https://marketplace.tf/items/30175;5;u17

Listed on Marketplace are three.

Using keys @ 1.89:

First listing is for 396.8 keys, unsold for almost 3 months

2nd listing is for 529.1 keys, unsold for 5 months

3rd listing is for 653.4 keys, unsold for a year+ (is duped)

https://bazaar.tf/search/?s=30175&sg=440&sp=quality=5,effect=17

Listed for a B/O of 600 keys on Bazaar.tf

http://www.tf2outpost.com/search/273110258

Listed for a B/O "quicksell' of 599 keys.

3 on Bp.tf:

1st listed for 610 keys, unsold for 6 months

2nd listed @ 615 keys, unsold for 2 years

3rd listed for 700 keys, unsold for 8 months

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Sale 1:

https://backpack.tf/profiles/76561197993708178#!/compare/1514505600/1515888000

Sold for Duped Scorching Veil

Veil Mini:

https://backpack.tf/profiles/76561198036102887#!/compare/1517616000/1517702400

https://backpack.tf/profiles/76561197993708178#!/compare/1517443200/1517702400

Sold for Aussie RL(33.5) + Slumber Mohawk(110) + Duped Burning Drill Hat(155) + Beams Batter(67) + Duped Burning Brigade Helm(147.5)

33.5 + 110 + 155 + 67 + 147.5 = 513 keys.

This is the only duped recent sale i can trace.

Valuing at 513 keys.

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Sale 2:

https://backpack.tf/profiles/76561198095236132#!/compare/1515801600/1515888000

https://backpack.tf/profiles/76561198139276623#!/compare/1515801600/1515888000

Sold with GF Heer Helmet for 216 keys pure

Not using sale, seems extremely low, cash may have been involved.

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Sale 3:

https://backpack.tf/profiles/76561198139276623#!/compare/1515888000/1515974400 Seller

https://backpack.tf/profiles/76561198138392299#!/compare/1515801600/1515974400 Buyer

Holy crap 1300+ items for the Sunbeams Cotton Head.

Items of note:

Hellish Skullcracker(24) + HHH Headtaker(3.6) + TF Logo Great Helm + TW Pom-Pommed Provocateur + Scorching Mirror + Ghastly Ghosts Jr Rotation Sensation (140)

Other items add up to approximately 289.43 keys, according to bp.tf.

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Great Helm Mini:

Only sale:

https://backpack.tf/profiles/76561198193200729#!/compare/1516406400/1516492800

Sold for Aussie Scatter-gun.

Valuing @ 23.58, rounding to 24.

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TW Pom-Pommed Provocateur Mini:

https://backpack.tf/profiles/76561198129760627#!/compare/1516060800/1516492800

https://backpack.tf/profiles/76561198087172601#!/compare/1516406400/1516492800

Sold for TW Conquistador(14).

then sold for DBD Nano(16).

https://backpack.tf/profiles/76561198107829703#!/compare/1516665600/1516752000

Sold for 13 pure.

https://backpack.tf/profiles/76561198290156699#!/compare/1516924800/1517097600

Sold for 11 pure.

https://backpack.tf/profiles/76561198044099975#!/compare/1515110400/1515369600

Sold for Vivid Robo-glove(20.5) + a key

https://backpack.tf/profiles/76561198449284561#!/compare/1513641600/1513728000

Sold for Planets Fed-Fightin'

Other Clean Fedora sales are only to bots, using 13 keys on account of this.

In Total: 11, 13, 13, 14, 16, 21.5.

Outlier is 21.5, setting price at 13-16. Averages out to 14.5 keys.

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Scorching Mirror Mini:

https://backpack.tf/profiles/76561198139276623#!/compare/1516060800/1516147200

https://backpack.tf/profiles/76561198304138933#!/compare/1516060800/1516147200

Sold to bot for 47 keys + 15 ref.

https://backpack.tf/profiles/76561198055721127#!/compare/1515888000/1515974400

Sold for Burning Gonzilla(55)

https://backpack.tf/profiles/76561198046643835#!/compare/1516060800/1517097600

Sold for 54 keys

47 is QS, using 54 + 55, rounding to 54 (pure > unusual)

=================================================================================

Total is 54 + 14.5 + 24 + 3.6 + 140 + 289.43 = 525.53 keys

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513 & 525.53.

Rounding to 515 & 525.

F⌬amy's Info:

That seller is still there and must definitely have been there at or closely around that value for well over a month now (perhaps even the entire time); with keys at 1.98$ that'd make for 385

https://backpack.tf/item/5287993705 History of the relevant item

By now that should be included in the range. Not opposed to a full range of 385-525 here, despite that being fairly wide.