A masterwork weapon.

Magic weapons have enhancement bonuses ranging from +1 to +5. They apply these bonuses to both attack and damage rolls when used in combat. All magic weapons are also masterwork weapons, but their masterwork bonus on attack rolls do not stack with their enhancement bonus on attack rolls.
+5 enhancement bonus adds 10 to a weapon's hardness and +50 to its hit points.

Prerequisites: Craft Magic Arms and Armor.
Cost to Create: 25,000 gp (plus 300 gp for base item), 2000 XP, 50 days.