Alot of buyers

Buyers:

http://www.tf2outpost.com/trade/22867576 - 4.66 (has plenty of metal)

http://www.tf2outpost.com/trade/23519822 - 4.33 (has plenty of metal)

http://www.tf2outpost.com/trade/13669092 - 4.33 (has plenty of metal)

http://www.tf2outpost.com/trade/23363165 - 4.11

http://www.tf2outpost.com/trade/6760241 - 4

http://www.tf2outpost.com/trade/17417942 - 4

And about a dozen other people on OP buying at 4 ref.

Sellers:

http://www.tf2outpost.com/trade/17162597 - 5 (1 in stock)

http://www.tf2outpost.com/trade/23667566 - 5 (1 in stock)

http://www.tf2outpost.com/trade/22867576 - 4.77 (out of stock)

http://www.tf2outpost.com/trade/22663642 - 4.77 (out of stock)

http://www.tf2outpost.com/trade/23501618 - 4.66 (out of stock)

http://backpack.tf/classifieds/?item=Squad%20Surplus%20Voucher&quality=6&tradable=1&craftable=0

- 1x seller (selling multiple) 4.88 ref

- 6x 5 ref

http://steamcommunity.com/market/listings/440/Squad%20Surplus%20Voucher

- Current and past sales at about 55% of the market's key price, or ~5.77 ref