Let's try this one.

One usable sale (other is being used for the modest):

Sold for a duped Beams Kabuto (170) + Spec KS Aussie Black Box (22) + Collectors DA (4) and RS (4)

170 + 4 + 4 * 0.9 + 22 = 182.2 keys rounding to 182 keys

http://www.tf2outpost.com/search/246850273 - Screenshots

http://backpack.tf/profiles/76561198052057273?time=1427958000

http://backpack.tf/profiles/76561198052057273?time=1429340400

Kabuto mini:

Sold with a duped secret Coupe for a Mega I see You (45) + Beams Yellow Belt (150) + Searing Swagmans (56) + Planets Veil (43)

150 + 56 + 43 + 45 - 35 = 259 keys

I don't believe this is accurate, but I am unable to use any of the other sales, as they all used unpriced hats, or I couldn't trace the traded items. Going with the current low end, supported by a current C/O (B/O?) on market.

http://backpack.tf/profiles/76561198101300189?time=1428649200

http://backpack.tf/profiles/76561198101300189?time=1428735600

Coupe mini:

Sold with a 13th Dixe (43) for a Blizzardy TC (78)

78 - 43 = 35 keys

http://backpack.tf/profiles/76561198070877812?time=1427007600

http://backpack.tf/profiles/76561198070877812?time=1427094000