Re-Re-Re-suggesting, following Polar's info.

Sale #1:

Sold on mp.tf, May 27, 2019 for $279.99

https://marketplace.tf/shopitem/76561198049278733/30362;5;u19;strange

Keys that day were $1.81:

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

$279.99/1.81= 154.69. Rounding to 155.

May look like quicksell- but with buyers at 101 keys, (http://prntscr.com/nwedxa), and other recent sales around this price, not considering this a quicksell.

Sale #2. (Invalid, ignoring- No mini on medigun, unable to create one.):

https://backpack.tf/profiles/76561198082401774#!/compare/1557964800/1558137600

Sale #3 (Not actually a sale- deposit into mp.tf, ignoring):

https://backpack.tf/profiles/76561198082401774#!/compare/1558396800/1558915200

Looks like this was the marketplace deposit. Sold on 27th. Comparing history confirms this. Hat appeared in inventory on 27th- same time the hat sold on marketplace.

https://backpack.tf/profiles/76561198049278733#!/compare/1558828800/1558915200

Sale #4:

Sold on mp.tf on June 6, 2019 for $300

https://marketplace.tf/items/30362;5;u19;strange/Strange%20Circling%20Heart%20Law

Keys that day were $1.79

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

$300/$1.79 = 167.59, rounding to 168

Sale #5

Sold on mp.tf on June 7, 2019 for $312

https://marketplace.tf/items/30362;5;u19;strange/Strange%20Circling%20Heart%20Law

Keys that day were $1.80

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

$312/$1.80 = 173.33, rounding to 173

Sale #6: (Excluding. Using this sale to price the Samureye)

Sold for a Robactive Samur-Eye:

https://backpack.tf/profiles/76561198065994454#!/compare/1560211200/1560297600

RA Samur-eye sugg:

https://backpack.tf/suggestion/5d08775567807226de72385b

Sale #7

Sold for a duped GE Team Captain. Outlier, ignoring.

https://scrap.tf/auctions/3CXWEY

Strangifier exists for this hat. Ignoring the fact that it sold as a Strange.

In conclusion: 155-173 keys.