Took a while.......

Sale 1: Seems Low.

Sold For Steaming Hat With No Name + 2 Keys?

https://backpack.tf/profiles/76561198967685813#!/compare/1561680000/1561766400

https://backpack.tf/profiles/76561198063107526#!/compare/1561680000/1561766400

Sale 2: ~31 Keys Pure.

https://backpack.tf/profiles/76561198063107526#!/compare/1561766400/1561852800

https://backpack.tf/profiles/76561198282471428#!/compare/1561766400/1561852800

Sale 3: ~31 Keys.

Sold For Max's Severed Head (21) + 10 Keys = 31 Keys.

https://backpack.tf/profiles/76561198282471428#!/compare/1561939200/1562025600

https://backpack.tf/profiles/76561198002391950#!/compare/1561248000/1562025600

Sale 4: Untrace.

https://backpack.tf/profiles/76561198002391950#!/compare/1562025600/1562630400 - 1 Key Match.

https://backpack.tf/profiles/76561198286234945#!/compare/1562544000/1562630400

Sale 5: Use There.

Sold For Molten Mallard Swagman's Swatter + 8 Keys.

https://backpack.tf/profiles/76561198286234945#!/compare/1562630400/1562716800

https://backpack.tf/profiles/76561198205939253#!/compare/1562630400/1562716800

Sale 6: Bulk.

https://backpack.tf/profiles/76561198205939253#!/compare/1563235200/1563321600

https://backpack.tf/profiles/76561198362008411#!/compare/1563235200/1563321600

Sale 7: Untrace.

https://backpack.tf/profiles/76561198362008411#!/compare/1563494400/1563580800

https://backpack.tf/profiles/76561197964546925#!/compare/1563148800/1563667200

Sale 8: Untrace.

https://backpack.tf/profiles/76561197966549202#!/compare/1557619200/1557705600

https://backpack.tf/profiles/76561198026129220#!/compare/1557619200/1557705600

Sale 9: Untrace.

https://backpack.tf/profiles/76561198026129220#!/compare/1557619200/1558137600

https://backpack.tf/profiles/76561198093031738#!/compare/1557619200/1558051200

Sale 10: Untrace.

https://backpack.tf/profiles/76561198026129220#!/compare/1557619200/1558137600

https://backpack.tf/profiles/76561198174748513#!/compare/1557792000/1558137600

Sale 11: Bulk.

https://backpack.tf/profiles/76561198342476957#!/compare/1560902400/1560988800

https://backpack.tf/profiles/76561198256998558#!/compare/1560902400/1560988800

Sale 12: ~40 Keys.

Sold For Cloudy Moon Prancer's Pride (47)

https://backpack.tf/profiles/76561198256998558#!/compare/1561248000/1561334400

https://backpack.tf/profiles/76561197995349934#!/compare/1561248000/1561334400

B/O was 40 keys - https://bot.tf/stats/listings/ML3182OY

Sale 13: ~29 Keys. (Calling Low)

https://backpack.tf/profiles/76561197995349934#!/compare/1561248000/1561334400

https://backpack.tf/profiles/76561198001665268#!/compare/1561248000/1561334400

Sale 13: ~40 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1561075200/1561161600

https://backpack.tf/profiles/76561198081907770#!/compare/1561075200/1561161600

https://gist.github.com/juliarose/7f45a54264f8961b91cb98605afeae60

https://gyazo.com/94ae3bf7654ce239092cd24214c3ad76 - 6/22/19

Sale 14: Untrace.

https://backpack.tf/profiles/76561198081907770#!/compare/1561766400/1563235200

https://backpack.tf/profiles/76561198080179568#!/compare/1561680000/1561766400

Sale 15: ~38 Keys Pure.

https://backpack.tf/profiles/76561198080179568#!/compare/1561939200/1562025600

https://backpack.tf/profiles/76561198036270946#!/compare/1562025600/1562112000

Sale 16: Untrace.

https://backpack.tf/profiles/76561198036270946#!/compare/1562112000/1562198400

https://backpack.tf/profiles/76561198080179568#!/compare/1562025600/1562112000

Sale 17: Untrace.

https://backpack.tf/profiles/76561198024867201#!/compare/1555977600/1556064000

https://backpack.tf/profiles/76561198860044620#!/compare/1554681600/1556064000

Marketplace.tf Sales: https://marketplace.tf/items/tf2/31010;5;u115

Sale 18: ~31 Keys.

May 13

$56.15 / $1.82 = 30.85 keys

Sale 19: ~55 Keys.

May 15

$99.99 / $1.82 = 54.94 keys (High)

Sale 20: ~32 Keys.

Jul 20

$57.10 / $1.81 = 31.55 keys

Sales: 29/31/31/31/32/38/40/40/55

Going with 31-40 keys.

Thanks to scourge for the premium!