Slight head start on these.

Sold for a Circling Peace Sign Buckaroos Hat(12 Keys with Overpay)

http://backpack.tf/profiles/76561198066207210?time=1446710400 (November 5th)

http://backpack.tf/profiles/76561198066207210?time=1446969600 (November 8th)

http://backpack.tf/profiles/76561198137408851?time=1446274800 (October 31st)

http://backpack.tf/profiles/76561198137408851?time=1446969600 (November 8th)

Sold for 9 Keys and ~1 Key in Sweets(10 Keys total)

http://backpack.tf/profiles/76561198203602999?time=1444287600 (October 8th)

http://backpack.tf/profiles/76561198203602999?time=1444374000 (October 9th)

Sold for a Blizzardy Storm Magistrate's Mullet(11 Keys with Overpay)

http://backpack.tf/profiles/76561198069263633?time=1448870400 (November 30th)

http://backpack.tf/profiles/76561198069263633?time=1448956800 (December 1st)

http://backpack.tf/profiles/76561198192602363?time=1448870400 (November 30th)

http://backpack.tf/profiles/76561198192602363?time=1448956800 (December 1st)

Sold for ~14 Keys in Items(13 Keys with Overpay)

http://backpack.tf/profiles/76561198108152326?time=1450771200 (December 22nd)

http://backpack.tf/profiles/76561198108152326?time=1450857600 (December 23rd)

http://backpack.tf/profiles/76561198114910392?time=1450425600 (December 18th)

http://backpack.tf/profiles/76561198114910392?time=1450857600 (December 23rd)

Sold for 10 Keys

http://backpack.tf/profiles/76561198141341262?time=1446102000 (October 29th)

http://backpack.tf/profiles/76561198141341262?time=1446188400 (October 30th)

Sales seem to fit, 10-13 Keys should be fine.

Additional Proof/Counter-Proof/Constructive Criticism/Feedback is always appreciated.