Risky but I'm gonna chance it :D (awful pun).

http://www.tf2outpost.com/trade/10467271 Was bought for a duped beams samur-eye + 2 pure (19-20ish in mixed, factoring unusual overpay)

http://www.tf2outpost.com/trade/10340673 C/Os include a ghosts executioner for it + 3 buds (The exe being 35 right now - 3 = 32 - unusual overpay = 28ish. Don't know how much it was worth back then). Another C/O is a beams samur-eye (duped) (17-19ish with overpay factorized).

http://www.tf2outpost.com/trade/10478648 You guessed it, another C/O of a beams samur-eye (17-19ish with overpay included)

http://www.tf2outpost.com/trade/10120442 Offers include 16 pure and the ghosts executioner for it + the p. energy pot + the smoking charmer's (Can't put a price on it, perhaps 23ish in unusuals with overpay reduction included)

Aware I need more sales proof but it's very iffy at the moment, the stuff on it is very unclear but I presume it's been focused around cash deals.

All B/Os have been 16-20 so far around this time, pretty fair to go to the middle spot and say 18.