Sale 1: ~10 Keys Pure.

https://backpack.tf/profiles/76561198343885717#!/compare/1554595200/1554681600

https://backpack.tf/profiles/76561198337734785#!/compare/1554595200/1554681600

Sale 2: Untrace. (SCM)

https://backpack.tf/profiles/76561198347306859#!/compare/1552694400/1555545600

https://backpack.tf/profiles/76561198408340108#!/compare/1551398400/1553904000

Sale 3: Untrace.

https://backpack.tf/profiles/76561198337734785#!/compare/1551830400/1551916800

https://backpack.tf/profiles/76561198898708893#!/compare/1552867200/1557964800

Sale 4: Untrace/Bulk.

https://backpack.tf/profiles/76561198070262319#!/compare/1556841600/1556928000

https://backpack.tf/profiles/76561198044684270#!/compare/1556841600/1556928000

Marketplace.tf Sales:

https://marketplace.tf/items/344;5;u35

Sale 5: High.

Mar 22

$29.99 / $1.8 = 16.66 keys

Sale 6: High.

Mar 28

$27.90 / $1.79 = 15.59 keys

Sale 7: ~10 Keys.

Apr 10

$18.06 / $1.77 = 10.20 keys

Bot.tf Sales:

https://bot.tf/stats/item?def=344&q=5&ef=Smoking&craft=1&aus=0&ks=0

~10 Keys.

(~11 keys) 2x

Including Sales: 10/10/10/11/11

Going With 10-11 Keys.

Thanks to scourge for the premium!