Sale 1:

Sold for 31 keys + ~1 key in metal in ~4 days

Seller: https://backpack.tf/profiles/76561198289040457#!/compare/1507507200/1507593600

Buyer: https://backpack.tf/profiles/76561198170859525#!/compare/1507507200/1507593600

X = 32

Sale 2:

Sold for 31 keys + 12 ref in ~1 day

Seller: https://backpack.tf/profiles/76561198375943285#!/compare/1507852800/1507939200

Buyer: https://backpack.tf/profiles/76561198219980724#!/compare/1507852800/1507939200

X = 31

Sale 3:

Sold for Australium Scattergun (~24)

Seller: https://backpack.tf/profiles/76561198026558681#!/compare/1509580800/1509667200

Buyer: https://backpack.tf/profiles/76561198050062763#!/compare/1509580800/1509667200

X = 24

Sale 4:

Sold for Mega Strike Burstchester

Seller: https://backpack.tf/profiles/76561198219980724#!/compare/1509148800/1509580800

Buyer: https://backpack.tf/profiles/76561198026558681#!/compare/1509321600/1509580800

Should be used on the burst.

Sellers:

36 keys:

https://i.imgur.com/7UwcwXR.png - most likely lowered/re-listed, given the history

https://backpack.tf/item/4308184440

Sales at:

24

31

32

31 quicksold, excluding 24 and 31.

Going with 32 flat.