Classifieds at the time of posting this suggestion.

x1 at 10 ref - http://i.imgur.com/gkHuizU.png

x1 at 10.66 ref - http://i.imgur.com/JBCaXxD.png

x6 at 10.77 ref, same seller - http://i.imgur.com/3eirL6l.png

x1 at 10.88 ref - http://i.imgur.com/lLdmfhy.png

x1 at 11 ref - http://i.imgur.com/hZPPcrR.png http://i.imgur.com/bK9aqfD.png

x1 at 11.33 ref - http://i.imgur.com/CzjesMR.png

x7 at 12 ref - http://i.imgur.com/rfr77xW.png http://i.imgur.com/1LciBqX.png

x2 at 13 ref - http://i.imgur.com/tJBgh6d.png

x1 at 16 ref - http://i.imgur.com/wBzDiGg.png

x2 at 2 keys - http://i.imgur.com/wsgTkuO.png

Buyers suggest 9 ref and below is the quickbuying price http://i.imgur.com/7E6eBmC.png

Sellers on Outpost

http://www.tf2outpost.com/trade/28341789 - 1 key, 2 days old - unsold for 2 weeks > http://www.tf2outpost.com/trade/28311147

http://www.tf2outpost.com/trade/28343641 - 12 ref, 1 day old.

http://www.tf2outpost.com/trade/28337672 - 12 ref, 4 days old.

http://www.tf2outpost.com/trade/28339776 - 11.66 ref, 3 days old - sellers seems to have quicksold it to a bot for 9 ref - http://i.imgur.com/pYtXCIg.png > http://www.tf2outpost.com/trade/27891280

http://www.tf2outpost.com/trade/28336990 - 11.66 ref, 4 days old.

http://www.tf2outpost.com/trade/28332887 - 11 ref, 6 days old, Autobumper.

Buyers on Outpost

http://www.tf2outpost.com/trade/27891280 - 9 ref, quickbuying bot.

I am excluding all sellers/buyers with their price as "bp.tf price" as the item has a flexible price making it an unclear price.

Many unsolds ranging from 10 ref to 13 ref. 10-12 ref seems reasonable.