New sales, new suggestion. Thanks to Torb for saving me from the ballcap mini. Three usable sales.

Sale #1 (Quicksell, ignoring):

Sold on mp.tf on May 8, 2019 for $47.

https://backpack.tf/profiles/76561198065400580#!/compare/1557273600/1557360000 (Buyer)

https://backpack.tf/profiles/76561198835360932#!/compare/1553731200/1557619200 (Seller- deposited into mp)

https://marketplace.tf/items/398;5;u14/Scorching%20Flames%20Doctor's%20Sack

Keys that day were $1.80

https://marketplace.tf/items/5021;6/Mann%20Co.%20Supply%20Crate%20Key

$47/1.8 = 26.1 keys. Below buy orders. Clearly a quicksell, ignoring.

Sale #2 (duped):

https://backpack.tf/profiles/76561198192602363#!/compare/1554076800/1554163200

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

Sold for 42 keys. Not excluding, as the dupe fits within the price range.

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.

Sale #4 (bulk, ignoring)

https://backpack.tf/profiles/76561198065400580#!/compare/1557619200/1557964800

Traded with SS Honcho's, Miami Jeepcap, GE Sensation for a SF Ninja Hood. Sack less than half the value of the trade- bulk.

Sale #5 (Bot deposit, ignoring)

https://backpack.tf/profiles/76561198142853906#!/compare/1557964800/1558051200

Sale #6 (Quicksell, ignoring)

https://backpack.tf/profiles/76561198081042493#!/compare/1558051200/1558137600

https://backpack.tf/profiles/76561198142853906#!/compare/1558051200/1558137600

Sold for 35 keys. Barely above buy order (http://prntscr.com/nx68gm)- considering quicksell- ignoring.

Sale #7 (bulk, ignoring)

https://backpack.tf/profiles/76561198081042493#!/compare/1559001600/1559088000

https://backpack.tf/profiles/76561198252999692#!/compare/1559001600/1559088000

Traded in bulk with other Unusuals for a GE Rotation Sensation. Sack less than half the value of the trade- bulk.

Sale #8 (clean)

https://backpack.tf/profiles/76561198192740165#!/compare/1559088000/1559174400

https://backpack.tf/profiles/76561198252999692#!/compare/1559088000/1559174400

Sold for a Orbiting Planets Detective Noir (13k), Bubbling Backwards Ball Cap (mini below), and 14 keys.

13 + 15 + 14 = 42 keys

Mini for Ballcap, thanks Torb

https://backpack.tf/suggestion/5cf57c7fd3817269d6504197

3 Sales @ 42 keys. I do love consistency.

In conclusion: 42 Keys.