Using last 2 months.

Sale #1:

https://backpack.tf/profiles/76561198104507776#!/compare/1549670400/1549929600

Sold for a Demonflame Hard Counter (49 keys)

No available mini for the Hard Counter. Possible sale at 48 keys, histories don't match though (https://backpack.tf/profiles/76561198258264645#!/compare/1545868800/1545955200).

49 keys

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Sale #2:

https://marketplace.tf/items/30672;5;u3016

Sold for $90.09.

$90.09 / $1.79 = ~50 keys

50 keys

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Sale #3:

https://marketplace.tf/items/30672;5;u3016

Sold for $91.

$91 / $1.79 = ~51 keys

51 keys