Update time, unlike valve with tf2. Thanks to shufflespy for their help.

Sale #1 (Likely a quicksell, ignoring):

Marketplace: Sold for $47.00

https://marketplace.tf/items/398;5;u14

Keys that day were $1.80

https://manic.tf/keyprice/?at=2019-05-08

47/1.80 = 26.11. Rounding to 26.

However, this is below buy orders.

http://prntscr.com/nnnoa4

Thus, ignoring Sale #1

Sale #2 (duped):

https://backpack.tf/profiles/76561198192602363#!/compare/1554076800/1554163200 (Sold for 42 keys)

https://backpack.tf/profiles/76561198264298268#!/compare/1554163200/1554249600 (The 43rd key is from the TOD tickets)

Sale #3 (clean):

https://backpack.tf/profiles/76561198192602363#!/compare/1553299200/1553385600

https://backpack.tf/profiles/76561198835360932#!/compare/1553299200/1553385600

Sold for 42 keys. The other doctor's sack you see is the duped one. Don't get confused.

Seller at 37:

http://prntscr.com/nnntdn

https://backpack.tf/item/921902243

In conclusion, going with 37-42