Sellers/solds for less than 5 keys

http://www.tf2outpost.com/trade/25189862 - Both sold for 9 keys (4.5 keys each) after being up for a month

Solds at 5 keys

http://www.tf2outpost.com/trade/23221985 - Managed to sell 2 recently for 5 keys each.

Unsolds at 5 keys

http://www.tf2outpost.com/trade/25528309 - 1 week

Classifieds

http://backpack.tf/stats/Unique/Strange%20Part%3A%20Damage%20Dealt/Tradable/Craftable -

x1 4.5 keys

x2 4.95 keys

Community Market

http://steamcommunity.com/market/listings/440/Strange%20Part%3A%20Damage%20Dealt - Multiple sales under 5 keys and 4 keys.

5 keys is still somewhat possible, but deteriorating. The others for sale are either extremely young, or unbumped. Very small market.