Sale 1:

Sold for 55 keys

Seller: https://backpack.tf/profiles/76561198313538268#!/compare/1551571200/1551657600

Buyer: https://backpack.tf/profiles/76561198220612564#!/compare/1551484800/1551657600

https://backpack.tf/item/531560434

X = 55

Sale 2:

Sold for 49 keys

Seller: https://backpack.tf/profiles/76561198061440669#!/compare/1550793600/1550880000

Buyer: https://backpack.tf/profiles/76561198261509772#!/compare/1550793600/1550880000

https://backpack.tf/item/398487026

https://bot.tf/stats/listings/M159J7X4 - B/O of 51

Checked the history of the key the shotgun was bought for to see if it was involved, but apparently not

https://backpack.tf/profiles/76561198195922917#!/compare/1550793600/1550880000

X = 49

Sale 3:

Sold to a bot for 43 keys

Seller: https://backpack.tf/profiles/76561198220612564#!/compare/1553385600/1553558400

Buyer: https://backpack.tf/profiles/76561198313538268#!/compare/1553472000/1553558400

https://backpack.tf/item/531560434

X = 43

Sales at:

43

49

55

No current sellers.

The buyer of the sale at 55 re-sold to the seller for 43. Excluding 55 as it was traded back, and excluding 43 as it sold to a bot/quickbuyer.

Going with 49 flat.