|Attack bonus if proficient||+3|
|Weapon die ([W])||1d6|
|Weapon properties|| defensive, off-hand (primary end)|
off-hand (secondary end)
The primary end of a double sword is a defensive weapon, so a character proficient with the double sword gains a +1 bonus to AC while wielding it. Both ends are off-hand weapons, so either end can be used to make attacks.
No class has proficiency with the double sword as a class trait, but any character can become proficient by taking a Weapon Proficiency feat.
The November 2009 rules update reduced the weapon die for both ends of the double sword from 1d8 to 1d6, changed its weapon groups from heavy blade and light blade to light blade only, and made only its primary end defensive.