Three recent histories. If refined has to be converted into keys, I'm using the current value of keys (62.22) because even back then the prices were highly above the backpack.tf price. Regardless, it will likely make little difference overall.

Sale 1:

https://backpack.tf/item/8651412561

https://backpack.tf/profiles/76561198064604036#!/compare/1602028800/1602201600

https://backpack.tf/profiles/76561198198970103#!/compare/1602374400/1602547200

Untraceable.

Sale 2:

https://backpack.tf/item/9260476730

https://backpack.tf/profiles/76561198095293350#!/compare/1601856000/1601942400

https://backpack.tf/profiles/76561199043625146#!/compare/1601856000/1601942400

Sold for The Eldritch Opening Highway Star + 17 keys.

Mini for The Eldritch Opening Highway Star:

https://marketplace.tf/items/tf2/31010;5;u115

October 28: $79.90 - $79.9 / $1.83 = 43.66 keys

November 16: $63 - $63 / $1.76 = 35.80 keys

Getting one trade sale to verify these sales: https://backpack.tf/item/7980227641

https://backpack.tf/profiles/76561198262422109#!/compare/1602201600/1602288000

https://backpack.tf/profiles/76561198047941585#!/compare/1602201600/1602288000

Sold for 35 keys. Buyer loses 41 keys, but even if it's 41 it's still within the 36-44 key range of MPTF.

Taking 40 keys as the value of The Eldritch Opening Highway Star.

The Classy Capper was therefore sold for 40+17=57 keys.

Sale 3:

https://backpack.tf/item/9260476730

https://backpack.tf/profiles/76561199043625146#!/compare/1601942400/1602028800

https://backpack.tf/profiles/76561198110216920#!/compare/1601942400/1602028800

Sold + Strange Rifleman's Regalia for 63 keys.

https://gyazo.com/0bcebf4dc9e23012986ba7fa5f034c6c

Valuing the Strange Rifleman's Regalia at 4.5 keys.

Valuing The Classy Capper in this trade at 63-4.5=58.5 keys (rounded to 59).

Sale 4:

https://marketplace.tf/items/tf2/30893;5;u17

October 13: $149

$149 / $1.89 = 78.84 keys

Sale 5:

https://marketplace.tf/items/tf2/30893;5;u17

October 22: $107

$107 / $1.85 = 57.84 keys

Sale 6:

https://backpack.tf/item/7149989954

https://backpack.tf/profiles/76561198045615120#!/compare/1603065600/1603152000

https://backpack.tf/profiles/76561199059840687#!/compare/1602720000/1603152000 - Can't find it in the buyer's inventory.

Looks like a QS at 32 keys 16.44 ref (0.26 keys), or otherwise untraceable.

Sale 7:

https://backpack.tf/item/7149989954

https://backpack.tf/profiles/76561199059840687#!/compare/1603152000/1603238400 - Can't find it in the seller's inventory

https://backpack.tf/profiles/76561198139171368#!/compare/1603065600/1603152000

1:2 for Scorching Flames Tippler's Tricorne + Burning Flames Backbiter's Billycock.

Mini for Scorching Flames Tippler's Tricorne:

https://backpack.tf/item/941912849

https://backpack.tf/profiles/76561198080275559#!/compare/1605830400/1605916800

https://backpack.tf/profiles/76561198337734785#!/compare/1605744000/1605830400

Sold for 50 keys, 1.11 ref (rounded to 50 keys)

Mini for Burning Flames Backbiter's Billycock:

https://backpack.tf/item/7669810819

https://backpack.tf/profiles/76561198141054773#!/compare/1604016000/1604102400

https://backpack.tf/profiles/76561198835556392#!/compare/1604016000/1604102400

Sold for 62 keys.

This values the Sunbeams Classy Capper at 50+62=112 keys.

Sale 8:

https://backpack.tf/item/7149989954

https://backpack.tf/profiles/76561198139171368#!/compare/1603411200/1603497600

https://backpack.tf/profiles/76561198415564349#!/compare/1603411200/1603497600

Bulk for Misty Skull Troublemaker's Tossle Cap, alongside Scorching Flames Helmet Without a Home + Cloud 9 Crone's Dome + Screaming Tiger Taunt: Battin' a Thousand + 4 keys.

Despite the fact we can't use this sale, it may give credence to sale 7 being too high. Valuing the Tossle Cap at 160 means the Cloud 9 Crone's Dome and Scorching Flames Helmet Without a Home (without doing minis) would be valued at less than 100 keys together.

Sale 9:

https://backpack.tf/item/7149989954

https://backpack.tf/profiles/76561198415564349#!/compare/1603584000/1603670400

https://backpack.tf/profiles/76561198186643130#!/compare/1603238400/1603756800

Sold for 70 keys. Buyer only sees 50 keys leave their inventory, but because they were not updated from the 21st to the 27th, it's likely the other 20 were simply never indexed.

Conclusion:

We have sales at: 57 keys, 59 keys, 78.84 keys (rounded to 79 keys), 57.84 keys (rounded to 58 keys), 32.26 keys (rounded to 32 keys), 112 keys, and 70 keys. We have an unsold at $210 for four months (https://gyazo.com/46e29b5a9909e000d7475365d34e6b81).

I'm going to exclude the 112 and 32 keys sales but include everything else in the range because of a) how similar it would make it with the current range, and b) because none are obvious outliers or too outrageous to include. Therefore, the range is 57-79 keys.