Not a lot of proof to be found (there never is with UCs). Most buyouts are around 1.33, and offers go between there and 1 ref. 1 - 1.33 ref sounds good to me.

http://www.tf2outpost.com/trade/7915732 - Offer of 1 ref, offer of 1.33 ref

http://www.tf2outpost.com/trade/8137786 - Selling for 1.33

http://www.tf2outpost.com/trade/8034860 - Willing to sell for 1.33

Bit tricky to price, 1 - 1.33 means that this is lower than the craftable one, and is represented by the offers and buyouts on Outpost.

Big thanks to Pomf | Woifi for the proof.