1 sold at 55 keys 24 ref (55.41 keys):

https://backpack.tf/profiles/76561198431421139#!/compare/1591488000/1591574400

https://backpack.tf/profiles/76561198305494036#!/compare/1591488000/1591574400

1 sold at 59 keys:

https://backpack.tf/profiles/76561198090869623#!/compare/1591833600/1592092800

https://backpack.tf/profiles/76561198305494036#!/compare/1592006400/1592092800

Sale on marketplace.tf at $77.20, May 22 2020 (median key price: $1.87, 77.2/1.87=41.28 keys)

https://marketplace.tf/items/tf2/30051;5;u13

55.41 keys and 41.28 keys are lower than buyers at 57.05 keys so they can't be used for the price, taking 59 keys as the price for my suggestion.

None have recently been bought or sold at 100 keys, so the price needs to be lowered