DUPED:

http://backpack.tf/profiles/76561198070115807?time=1405062000 - dp tc + smoking pusher ~8.5? can't tell if anything else added

http://www.tf2outpost.com/trade/20855218 - sold for an unusual taunt

http://www.tf2outpost.com/trade/20663293 4:1 ~9

http://backpack.tf/profiles/76561198066350638?time=1401606000 - gbh hallmark, unpriced (b/os on the market at 8-8.5)

http://www.tf2outpost.com/trade/19355268 - i don't know where you are getting this sale from, but this is the one that sold for the hallmark I listed above. His b/o was also 10 in pure.

http://www.tf2outpost.com/trade/21147929 - b/o 10

Lastly, DP hallmark value at the time of the sale. Sale happened on April 17?

Sales of the hallmark around that time:

April 19: http://www.tf2outpost.com/trade/19119461 - misty ten gallon ~7

April 5: http://www.tf2outpost.com/trade/18976559 - C9 hwnn + 3 ~7.3

April 4: http://www.tf2outpost.com/trade/18974002 - GE hallmark ~5.5

It would be generous calling that 7-8 at the time. Definitely wasn't 12.

Range for the duped 13th hour tyro is probably 8-9ish. Not really fair to price it on the duped one because a clean one has recently sold: http://backpack.tf/item/1214024063