I forgot what I was going to write here.

Sale #1: 28 keys,

http://www.tf2outpost.com/trade/28100352 - Sold w/Gen Robo-Sandvich (17.2) + 10 keys, for GBH Samur-Eye (56).

http://backpack.tf/profiles/76561197961465738#!/compare/1463788800/1463875200 (Seller)

http://backpack.tf/profiles/76561198070236972#!/compare/1463788800/1463875200 (Buyer)

Samur-Eye had B/O of 55.

55-27.2 = 27.8, rounding to 28.

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No other traceable sales found. 2 current sellers @ 27 and 28.

http://www.tf2outpost.com/search/264207868

https://gyazo.com/eae50544d3ff0542e445ec8005fcaa26

Suggesting at 28 flat, and as always feedback is appreciated.