From the DMG:
Does this mean that on a sneak attack the bonuses increase to +4 to attack and damage, or that they are added to the sword's existing +1 bonus? We've been playing it as the former, but actually reading the description I'm inclined to think it's the latter since the +4 bonuses are not named.
Sword of Subtlety
A +1 short sword with a thin, dull gray blade, this weapon provides a +4 bonus on its wielder’s attack and damage rolls when he is making a sneak attack with it.
Does this mean that on a sneak attack the bonuses increase to +4 to attack and damage, or that they are added to the sword's existing +1 bonus? We've been playing it as the former, but actually reading the description I'm inclined to think it's the latter since the +4 bonuses are not named.