Resuggesting, thanks Shuffle.

Sale 1: Unknown

https://backpack.tf/profiles/76561198053720151#!/compare/1585612800/1585699200

https://backpack.tf/profiles/76561198080179568#!/compare/1585612800/1585526400

Likely a quickbuy

Sale 2: Bulk?

https://backpack.tf/profiles/76561198311498888#!/compare/1585526400/1585612800

https://backpack.tf/profiles/76561198171672427#!/compare/1583280000/1585612800

Sale 3: Sold with Circling TF Logo Surgeon's Stahlhelm for keys

https://backpack.tf/profiles/76561198295224262#!/compare/1584230400/1584489600

https://backpack.tf/profiles/76561198311498888#!/compare/1584144000/1584230400

Sale 4: Sold for $92.92 on February 18, 2020

https://marketplace.tf/items/tf2/53;5;u9

$92.92 / $1.77 = 52.49 rounding to 52 keys

Sale 5: Sold for $110.83 on April 14, 2020

https://marketplace.tf/items/tf2/53;5;u9

$110.83 / $1.75 = 63.33 rounding to 63 keys

Sale 6: Sold for 49 keys

https://backpack.tf/profiles/76561198080179568#!/compare/1588032000/1588118400

Sales at 49, 52, and 63. Since 49 took a month to sell, 63 seems to be high.

Taking a range of 49-52 keys here.